Fix choppy YouTube video playback in Firefox and firefox-esr in Debian Bullseye - Unix & Linux Stack Exchange https://unix.stackexchange.com/questions/723814/how-to-fix-choppy-youtube-video-playback-enable-webrender-debian-bullseye
I hate to say it, but I decided to try Google Chrome in a Flatpak, and it runs a lot better than Vivaldi, which SHOULD be in a Flatpak at this point (but is not).