Eclipse Community

For what it's worth, here is an extension to block the use of some video codecs on Youtube (VP8, VP9 and AV1 by default) and also some other features (60 FPS, OPUS, Loudness normalization).
It can be useful with some old graphics cards which support hardware acceleration for H.264/AVC but not for recent codecs.

https://addons.mozilla.org/en-US/firefox/addon/enhanced-h264ify/

GitHub:
https://github.com/alextrv/enhanced-h264ify