diff --git a/.mypy.ini b/.mypy.ini
index 7bcf5f72..82321070 100644
--- a/.mypy.ini
+++ b/.mypy.ini
@@ -3,11 +3,16 @@
 # SPDX-License-Identifier: GPL-3.0-or-later
 
 [mypy]
-# check_untyped_defs = True
+check_untyped_defs = True
 # disallow_untyped_defs = True -- not yet feasible
 
-# strict = True -- only try to enable once everything is typed
+# strict = True -- only try to enable once everything (including dependencies!) is typed
 strict_equality = True
+strict_bytes = True
+
+warn_redundant_casts = True
+# warn_return_any = True
+warn_unreachable = True
 
 [mypy-ansible.*]
 # ansible-core has no typing information
diff --git a/plugins/module_utils/_acme/account.py b/plugins/module_utils/_acme/account.py
index 0b61e7f1..498bcbaa 100644
--- a/plugins/module_utils/_acme/account.py
+++ b/plugins/module_utils/_acme/account.py
@@ -176,6 +176,7 @@ class ACMEAccount:
         # check whether that failed with a malformed request error
         if (
             info["status"] >= 400
+            and isinstance(result, Mapping)
             and result.get("type") == "urn:ietf:params:acme:error:malformed"
         ):
             # retry as a regular POST (with no changed data) for pre-draft-15 ACME servers
@@ -183,7 +184,7 @@ class ACMEAccount:
             result, info = self.client.send_signed_request(
                 self.client.account_uri, data, fail_on_error=False
             )
-        if not isinstance(result, Mapping):
+        if not isinstance(result, dict):
             raise ACMEProtocolException(
                 module=self.client.module,
                 msg="Invalid account data retrieved from ACME server",
@@ -328,16 +329,17 @@ class ACMEAccount:
             account_data = dict(account_data)
             account_data.update(update_request)
         else:
-            account_data, info = self.client.send_signed_request(
+            raw_account_data, info = self.client.send_signed_request(
                 self.client.account_uri, update_request
             )
-            if not isinstance(account_data, Mapping):
+            if not isinstance(raw_account_data, Mapping):
                 raise ACMEProtocolException(
                     module=self.client.module,
                     msg="Invalid account updating reply from ACME server",
                     info=info,
                     content_json=account_data,
                 )
+            account_data = raw_account_data
 
         return True, account_data
 
diff --git a/plugins/module_utils/_acme/acme.py b/plugins/module_utils/_acme/acme.py
index 94039a57..b09c2e8c 100644
--- a/plugins/module_utils/_acme/acme.py
+++ b/plugins/module_utils/_acme/acme.py
@@ -343,7 +343,7 @@ class ACMEClient:
         fail_on_error: bool = True,
         error_msg: str | None = None,
         expected_status_codes: t.Iterable[int] | None = None,
-    ) -> tuple[dict[str, t.Any], dict[str, t.Any]]: ...
+    ) -> tuple[dict[str, t.Any] | bytes, dict[str, t.Any]]: ...
 
     @t.overload
     def send_signed_request(
diff --git a/plugins/module_utils/_acme/backend_cryptography.py b/plugins/module_utils/_acme/backend_cryptography.py
index a1e51201..003f5e37 100644
--- a/plugins/module_utils/_acme/backend_cryptography.py
+++ b/plugins/module_utils/_acme/backend_cryptography.py
@@ -102,14 +102,9 @@ class CryptographyChainMatcher(ChainMatcher):
             try:
                 return binascii.unhexlify(key_identifier.replace(":", ""))
             except Exception:
-                if criterium_idx is None:
-                    module.warn(
-                        f"Criterium has invalid {name} value. Ignoring criterium."
-                    )
-                else:
-                    module.warn(
-                        f"Criterium {criterium_idx} in select_chain has invalid {name} value. Ignoring criterium."
-                    )
+                module.warn(
+                    f"Criterium {criterium_idx} in select_chain has invalid {name} value. Ignoring criterium."
+                )
         return None
 
     def __init__(self, *, criterium: Criterium, module: AnsibleModule) -> None:
diff --git a/plugins/module_utils/_acme/challenges.py b/plugins/module_utils/_acme/challenges.py
index c00df34b..67fe0702 100644
--- a/plugins/module_utils/_acme/challenges.py
+++ b/plugins/module_utils/_acme/challenges.py
@@ -236,6 +236,12 @@ class Authorization:
             error_msg="Failed to request challenges",
             expected_status_codes=[200, 201],
         )
+        if not isinstance(result, dict):
+            raise ACMEProtocolException(
+                module=client.module,
+                msg="Unexpected authorization creation result",
+                content_json=result,
+            )
         return cls.from_json(client=client, data=result, url=info["location"])
 
     @property
@@ -358,7 +364,11 @@ class Authorization:
         result, info = client.send_signed_request(
             self.url, authz_deactivate, fail_on_error=False
         )
-        if 200 <= info["status"] < 300 and result.get("status") == "deactivated":
+        if (
+            200 <= info["status"] < 300
+            and isinstance(result, dict)
+            and result.get("status") == "deactivated"
+        ):
             self.status = "deactivated"
             return True
         return False
@@ -377,6 +387,12 @@ class Authorization:
         result, _info = client.send_signed_request(
             url, authz_deactivate, fail_on_error=True
         )
+        if not isinstance(result, dict):
+            raise ACMEProtocolException(
+                module=client.module,
+                msg="Unexpected challenge deactivation result",
+                content_json=result,
+            )
         authz._setup(client=client, data=result)
         return authz
 
diff --git a/plugins/module_utils/_acme/errors.py b/plugins/module_utils/_acme/errors.py
index 55474209..bff4ef31 100644
--- a/plugins/module_utils/_acme/errors.py
+++ b/plugins/module_utils/_acme/errors.py
@@ -72,7 +72,7 @@ class ACMEProtocolException(ModuleFailException):
         info: dict[str, t.Any] | None = None,
         response=None,
         content: bytes | None = None,
-        content_json: dict[str, t.Any] | None = None,
+        content_json: dict[str, t.Any] | bytes | None = None,
         extras: dict[str, t.Any] | None = None,
     ):
         # Try to get hold of content, if response is given and content is not provided
@@ -88,15 +88,18 @@ class ACMEProtocolException(ModuleFailException):
                     content = info.pop("body", None)
 
         # Make sure that content_json is None or a dictionary
+        content_json_json: dict[str, t.Any] | None = None
         if content_json is not None and not isinstance(content_json, dict):
             if content is None and isinstance(content_json, bytes):
                 content = content_json
             content_json = None
+        elif content_json is not None:
+            content_json_json = content_json.copy()
 
         # Try to get hold of JSON decoded content, when content is given and JSON not provided
-        if content_json is None and content is not None and module is not None:
+        if content_json_json is None and content is not None and module is not None:
             try:
-                content_json = module.from_json(to_text(content))
+                content_json_json = module.from_json(to_text(content))
             except Exception:
                 pass
 
@@ -117,19 +120,22 @@ class ACMEProtocolException(ModuleFailException):
             if (
                 code is not None
                 and code >= 400
-                and content_json is not None
-                and "type" in content_json
+                and content_json_json is not None
+                and "type" in content_json_json
             ):
-                error_type = content_json["type"]
-                if "status" in content_json and content_json["status"] != code:
-                    code_msg = f"status {content_json['status']} (HTTP status: {format_http_status(code)})"
+                error_type = content_json_json["type"]
+                if (
+                    "status" in content_json_json
+                    and content_json_json["status"] != code
+                ):
+                    code_msg = f"status {content_json_json['status']} (HTTP status: {format_http_status(code)})"
                 else:
                     code_msg = f"status {format_http_status(code)}"
                     if code == -1 and info.get("msg"):
                         code_msg = f"error: {info['msg']}"
-                subproblems = content_json.pop("subproblems", None)
-                add_msg = f" {format_error_problem(content_json)}."
-                extras["problem"] = content_json
+                subproblems = content_json_json.pop("subproblems", None)
+                add_msg = f" {format_error_problem(content_json_json)}."
+                extras["problem"] = content_json_json
                 extras["subproblems"] = subproblems or []
                 if subproblems is not None:
                     add_msg = f"{add_msg} Subproblems:"
@@ -142,13 +148,13 @@ class ACMEProtocolException(ModuleFailException):
                 code_msg = f"HTTP status {format_http_status(code)}"
                 if code == -1 and info.get("msg"):
                     code_msg = f"error: {info['msg']}"
-                if content_json is not None:
-                    add_msg = f" The JSON error result: {content_json}"
+                if content_json_json is not None:
+                    add_msg = f" The JSON error result: {content_json_json}"
                 elif content is not None:
                     add_msg = f" The raw error result: {to_text(content)}"
             msg = f"{msg} for {url} with {code_msg}"
-        elif content_json is not None:
-            add_msg = f" The JSON result: {content_json}"
+        elif content_json_json is not None:
+            add_msg = f" The JSON result: {content_json_json}"
         elif content is not None:
             add_msg = f" The raw result: {to_text(content)}"
 
diff --git a/plugins/module_utils/_acme/orders.py b/plugins/module_utils/_acme/orders.py
index 59cd2a75..95990ab4 100644
--- a/plugins/module_utils/_acme/orders.py
+++ b/plugins/module_utils/_acme/orders.py
@@ -39,11 +39,11 @@ class Order:
 
         self.data: dict[str, t.Any] | None = None
 
-        self.status = None
+        self.status: str | None = None
         self.identifiers: list[tuple[str, str]] = []
-        self.replaces_cert_id = None
-        self.finalize_uri = None
-        self.certificate_uri = None
+        self.replaces_cert_id: str | None = None
+        self.finalize_uri: str | None = None
+        self.certificate_uri: str | None = None
         self.authorization_uris: list[str] = []
         self.authorizations: dict[str, Authorization] = {}
 
@@ -106,6 +106,12 @@ class Order:
             error_msg="Failed to start new order",
             expected_status_codes=[201],
         )
+        if not isinstance(result, dict):
+            raise ACMEProtocolException(
+                module=client.module,
+                msg="Unexpected new order response",
+                content_json=result,
+            )
         return cls.from_json(client=client, data=result, url=info["location"])
 
     @classmethod
diff --git a/plugins/module_utils/_crypto/_obj2txt.py b/plugins/module_utils/_crypto/_obj2txt.py
index d0872cb2..5a356572 100644
--- a/plugins/module_utils/_crypto/_obj2txt.py
+++ b/plugins/module_utils/_crypto/_obj2txt.py
@@ -57,7 +57,8 @@ def obj2txt(openssl_lib, openssl_ffi, obj) -> str:
         buf_len = res + 1
         buf = openssl_ffi.new("char[]", buf_len)
         res = openssl_lib.OBJ_obj2txt(buf, buf_len, obj, 1)
-    return openssl_ffi.buffer(buf, res)[:].decode()
+    bytes_str: bytes = openssl_ffi.buffer(buf, res)[:]
+    return bytes_str.decode()
 
 
 __all__ = ("obj2txt",)
diff --git a/plugins/module_utils/_crypto/cryptography_support.py b/plugins/module_utils/_crypto/cryptography_support.py
index 85fd02e3..8c4c648a 100644
--- a/plugins/module_utils/_crypto/cryptography_support.py
+++ b/plugins/module_utils/_crypto/cryptography_support.py
@@ -287,8 +287,6 @@ def cryptography_oid_to_name(
 
 
 def _get_hex(bytesstr: bytes) -> str:
-    if bytesstr is None:
-        return bytesstr
     data = binascii.hexlify(bytesstr)
     return to_text(b":".join(data[i : i + 2] for i in range(0, len(data), 2)))
 
@@ -863,7 +861,7 @@ def parse_pkcs12(
     if _load_pkcs12 is not None:
         return _parse_pkcs12_36_0_0(pkcs12_bytes, passphrase=passphrase_bytes)
 
-    if LooseVersion(cryptography.__version__) >= LooseVersion("35.0"):
+    if LooseVersion(cryptography.__version__) >= LooseVersion("35.0"):  # type: ignore[unreachable]
         return _parse_pkcs12_35_0_0(pkcs12_bytes, passphrase=passphrase_bytes)
 
     return _parse_pkcs12_legacy(pkcs12_bytes, passphrase=passphrase_bytes)
diff --git a/plugins/module_utils/_crypto/module_backends/certificate_info.py b/plugins/module_utils/_crypto/module_backends/certificate_info.py
index 5ce816e3..2e0206d6 100644
--- a/plugins/module_utils/_crypto/module_backends/certificate_info.py
+++ b/plugins/module_utils/_crypto/module_backends/certificate_info.py
@@ -281,7 +281,7 @@ class CertificateInfoRetrievalCryptography(CertificateInfoRetrieval):
             return 1
         if self.cert.version == x509.Version.v3:
             return 3
-        return "unknown"
+        return "unknown"  # type: ignore[unreachable]
 
     def _get_key_usage(self) -> tuple[list[str] | None, bool]:
         try:
diff --git a/plugins/module_utils/_crypto/module_backends/csr.py b/plugins/module_utils/_crypto/module_backends/csr.py
index fdd385f9..eb51e04c 100644
--- a/plugins/module_utils/_crypto/module_backends/csr.py
+++ b/plugins/module_utils/_crypto/module_backends/csr.py
@@ -133,7 +133,7 @@ class CertificateSigningRequestBackend(metaclass=abc.ABCMeta):
         self.authority_cert_issuer: list[str] | None = module.params[
             "authority_cert_issuer"
         ]
-        self.authority_cert_serial_number: int = module.params[
+        self.authority_cert_serial_number: int | None = module.params[
             "authority_cert_serial_number"
         ]
         self.crl_distribution_points: (
@@ -361,10 +361,6 @@ def parse_crl_distribution_points(
 class CertificateSigningRequestCryptographyBackend(CertificateSigningRequestBackend):
     def __init__(self, *, module: AnsibleModule) -> None:
         super().__init__(module=module)
-        if self.version != 1:
-            module.warn(
-                "The cryptography backend only supports version 1. (The only valid value according to RFC 2986.)"
-            )
 
         crl_distribution_points: list[dict[str, t.Any]] | None = module.params[
             "crl_distribution_points"
diff --git a/plugins/module_utils/_crypto/module_backends/privatekey.py b/plugins/module_utils/_crypto/module_backends/privatekey.py
index 790374a2..179b8e01 100644
--- a/plugins/module_utils/_crypto/module_backends/privatekey.py
+++ b/plugins/module_utils/_crypto/module_backends/privatekey.py
@@ -287,7 +287,9 @@ class _Curve:
     def _get_ec_class(
         self, *, module: GeneralAnsibleModule
     ) -> type[cryptography.hazmat.primitives.asymmetric.ec.EllipticCurve]:
-        ecclass = cryptography.hazmat.primitives.asymmetric.ec.__dict__.get(self.ectype)  # type: ignore
+        ecclass: (
+            type[cryptography.hazmat.primitives.asymmetric.ec.EllipticCurve] | None
+        ) = cryptography.hazmat.primitives.asymmetric.ec.__dict__.get(self.ectype)
         if ecclass is None:
             module.fail_json(
                 msg=f"Your cryptography version does not support {self.ectype}"
diff --git a/plugins/module_utils/_openssh/backends/keypair_backend.py b/plugins/module_utils/_openssh/backends/keypair_backend.py
index 652e9b3e..22e4ea1b 100644
--- a/plugins/module_utils/_openssh/backends/keypair_backend.py
+++ b/plugins/module_utils/_openssh/backends/keypair_backend.py
@@ -285,7 +285,7 @@ class KeypairBackend(OpensshModule, metaclass=abc.ABCMeta):
             self._update_comment()
 
     def _create_temp_public_key(self, content: str | bytes) -> str:
-        temp_public_key = os.path.join(
+        temp_public_key: str = os.path.join(
             self.module.tmpdir, os.path.basename(self.public_key_path)
         )
 
diff --git a/plugins/module_utils/_openssh/utils.py b/plugins/module_utils/_openssh/utils.py
index 452f5c8c..9d29a3b8 100644
--- a/plugins/module_utils/_openssh/utils.py
+++ b/plugins/module_utils/_openssh/utils.py
@@ -101,21 +101,21 @@ class OpensshParser:
     def boolean(self) -> bool:
         next_pos = self._check_position(self.BOOLEAN_OFFSET)
 
-        value = _BOOLEAN.unpack(self._data[self._pos : next_pos])[0]
+        value: bool = _BOOLEAN.unpack(self._data[self._pos : next_pos])[0]
         self._pos = next_pos
         return value
 
     def uint32(self) -> int:
         next_pos = self._check_position(self.UINT32_OFFSET)
 
-        value = _UINT32.unpack(self._data[self._pos : next_pos])[0]
+        value: int = _UINT32.unpack(self._data[self._pos : next_pos])[0]
         self._pos = next_pos
         return value
 
     def uint64(self) -> int:
         next_pos = self._check_position(self.UINT64_OFFSET)
 
-        value = _UINT64.unpack(self._data[self._pos : next_pos])[0]
+        value: int = _UINT64.unpack(self._data[self._pos : next_pos])[0]
         self._pos = next_pos
         return value
 
diff --git a/plugins/modules/acme_certificate.py b/plugins/modules/acme_certificate.py
index 8d954c5f..1276ab0e 100644
--- a/plugins/modules/acme_certificate.py
+++ b/plugins/modules/acme_certificate.py
@@ -634,7 +634,7 @@ class ACMECertificateClient:
         self.cert_days = -1
         self.order: Order | None = None
         self.order_uri = self.data.get("order_uri") if self.data else None
-        self.all_chains = None
+        self.all_chains: list[dict[str, t.Any]] | None = None
         self.select_chain_matcher = []
         self.include_renewal_cert_id = module.params["include_renewal_cert_id"]
         self.profile = module.params["profile"]
diff --git a/plugins/modules/acme_certificate_revoke.py b/plugins/modules/acme_certificate_revoke.py
index 1a883919..a6a42ee9 100644
--- a/plugins/modules/acme_certificate_revoke.py
+++ b/plugins/modules/acme_certificate_revoke.py
@@ -217,12 +217,16 @@ def main() -> t.NoReturn:
         if info["status"] != 200:
             already_revoked = False
             # Standardized error from draft 14 on (https://tools.ietf.org/html/rfc8555#section-7.6)
-            if result.get("type") == "urn:ietf:params:acme:error:alreadyRevoked":
+            if (
+                isinstance(result, dict)
+                and result.get("type") == "urn:ietf:params:acme:error:alreadyRevoked"
+            ):
                 already_revoked = True
             else:
                 # Hack for Boulder errors
                 if (
-                    result.get("type") == "urn:ietf:params:acme:error:malformed"
+                    isinstance(result, dict)
+                    and result.get("type") == "urn:ietf:params:acme:error:malformed"
                     and result.get("detail") == "Certificate already revoked"
                 ):
                     # Fallback: boulder returns this in case the certificate was already revoked.
diff --git a/plugins/modules/get_certificate.py b/plugins/modules/get_certificate.py
index abe2a61c..55ff7399 100644
--- a/plugins/modules/get_certificate.py
+++ b/plugins/modules/get_certificate.py
@@ -440,7 +440,7 @@ def main() -> t.NoReturn:
                     module.fail_json(
                         msg=f"tls_ctx_options must be a string or integer, got {tls_ctx_option!r}"
                     )
-                    tls_ctx_option_int = (
+                    tls_ctx_option_int = (  # type: ignore[unreachable]
                         0  # make pylint happy; this code is actually unreachable
                     )
 
@@ -558,7 +558,7 @@ def main() -> t.NoReturn:
     elif x509.version == cryptography.x509.Version.v3:
         result["version"] = 3 - 1
     else:
-        result["version"] = "unknown"
+        result["version"] = "unknown"  # type: ignore[unreachable]
 
     if verified_chain is not None:
         result["verified_chain"] = verified_chain
diff --git a/plugins/modules/luks_device.py b/plugins/modules/luks_device.py
index e10a9ef4..d0a47977 100644
--- a/plugins/modules/luks_device.py
+++ b/plugins/modules/luks_device.py
@@ -510,9 +510,6 @@ class Handler:
     def get_device_by_label(self, label: str) -> str | None:
         """Returns the device that holds label passed by user"""
         blkid_bin = self._module.get_bin_path("blkid", True)
-        label = self._module.params["label"]
-        if label is None:
-            return None
         rc, stdout, dummy = self._run_command([blkid_bin, "--label", label])
         if rc != 0:
             return None
diff --git a/plugins/modules/openssl_pkcs12.py b/plugins/modules/openssl_pkcs12.py
index 548e9e24..05e2fc8b 100644
--- a/plugins/modules/openssl_pkcs12.py
+++ b/plugins/modules/openssl_pkcs12.py
@@ -529,13 +529,8 @@ class Pkcs(OpenSSLObject):
             elif bool(pkcs12_certificate) != bool(self.certificate_content):
                 return False
 
-            if (pkcs12_other_certificates is not None) and (
-                self.other_certificates is not None
-            ):
-                expected_other_certs = self._dump_other_certificates(self.pkcs12)
-                if set(pkcs12_other_certificates) != set(expected_other_certs):
-                    return False
-            elif bool(pkcs12_other_certificates) != bool(self.other_certificates):
+            expected_other_certs = self._dump_other_certificates(self.pkcs12)
+            if set(pkcs12_other_certificates) != set(expected_other_certs):
                 return False
 
             if pkcs12_privatekey:
diff --git a/plugins/modules/x509_certificate.py b/plugins/modules/x509_certificate.py
index 1edfa9b1..7eda271c 100644
--- a/plugins/modules/x509_certificate.py
+++ b/plugins/modules/x509_certificate.py
@@ -293,7 +293,7 @@ class GenericCertificate(OpenSSLObject):
         self.module = module
         self.return_content = module.params["return_content"]
         self.backup = module.params["backup"]
-        self.backup_file = None
+        self.backup_file: str | None = None
 
         self.module_backend = module_backend
         self.module_backend.set_existing(