Opera H.264 support (ffmpeg, streaming)

Is there a way to enable this codec support for Opera?

I installed opera via nix-env. As far as I understand, it needs ffmpeg to be available, which I see here as well:


But if I go to html5test.com the support wont be available (hence, no youtube streams).
As well I can not install chromium-codecs-ffmpeg (or vivaldi-codecs-ffmpeg, as how it is called now) since this conflicts with the .so file that I mentioned above.

Any idea?
Thanks a lot in advance!

I just tried Opera 68.0.3618.63, and Youtube works even though html5test.com says there’s no support for H264. It looks like ffmpeg is included:

❯ nix build -f default opera && find -L ./result | grep ffmpeg

Yes, normal Youtube Videos work. It’s the streams that are not available.