I've force-pushed with a patch that downgrades the minversion of pytest set in pyproject.toml, as pytest in the repos here is still on 8.3.4. That should fix the check issues.

See
streamlink/streamlink#6612
streamlink/streamlink#6727

Please drop the extra body text of your commit message, leaving only the first line. Also, it would be better if your patch just drops minimum version restrictions on pytest, because the environment will get whatever we provide.

No, the entire addopts needs to be removed if you want to run tests with pytest 8.3.x (the current state of your package repo).

The --disable-plugin-autoload pytest parameter that's part of the addopts field was added in pytest 8.4.0, which is the entire reason for this patch, to make it compatible. Whatever is added by your test scripts is irrelevant.
https://docs.pytest.org/en/latest/changelog.html#pytest-8-4-0-2025-06-02

Example if you just modify the minversion field:

diff --git a/pyproject.toml b/pyproject.toml
index 93c747e5..4fdedc6d 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -190,7 +190,7 @@ method = { module = "build_backend.onbuild", value = "onbuild" }
 # https://docs.pytest.org/en/latest/reference/customize.html#configuration
 # https://docs.pytest.org/en/latest/reference/reference.html#ini-options-ref
 [tool.pytest.ini_options]
-minversion = "8.4.0"
+minversion = "8.3.0"
 addopts = """
 --disable-plugin-autoload
 -p trio

$ pip list --format=json | jq '.[] | select(.name=="pytest")'
{
  "name": "pytest",
  "version": "8.3.4"
}

$ pytest
ERROR: usage: pytest [options] [file_or_dir] [file_or_dir] [...]
pytest: error: unrecognized arguments: --disable-plugin-autoload
  inifile: /home/basti/repos/streamlink/pyproject.toml
  rootdir: /home/basti/repos/streamlink

I haven't been clear. I understand that the addopts field must be patched out. In addition, it would be better to remove the minimum version altogether, rather than changing it to specify an arbitrary version not greater than what we ship.