Still WRONG! Ren'Py never use a CODECS but use ffmpeg to play video, that's it!
See the Ren'py documentation about movie...
Wrong saying that doesn't support mkv? ... no wait, that was you.
Anyway, genius, ffmpeg uses installed codecs(of course it does, what else would it use?). ffmpeg even comes bundled with the K-Lite and can be set as render engine for Windows Media Player Classic HC.
You would never say a game does not need C++ because it runs on UE5, even if UE5 requires C++, right?
By stating that Ren'Py uses ffmpeg you just proved the usefulness of installing additional codecs. ffmpeg will use them.