Okay, this build restored the video playback functionality but the performance is horrible running at only few FPS, now including other web-sites as well, like YouTube with vp9 and ac1 codecs. This is on RX 6700XT.
Please file that at bugzilla.redhat.com. I don't see that on RX 6600XT. Also we're supposed to switch to SW decode when VA-API fails.
I tested the update from 100 to 101 and the plugin is not changed. Looks like the change was made in some previous version. You need to go to about:config, find gmpopenh264 keys and reset them to default values. media.gmp-gmpopenh264.version needs to be system-installed. also make sure mozilla-openh264 package is installed (it's optional).