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
Due to server slowness, downtime, and other issues, guests can no longer search the forum or view user accounts. At some point in the future Eclipse will be moving to a more stable and efficient platform that should result in much better stability and the lifting of these restrictions. There is no timeline for this yet, just want you to know what's happening with all the downtime and I have a plan to fix it.