Hi all, fresh Endeavour install using the online installer and going with GNOME.
Had video and audio out of sync when playing back from browser (either firefox or chromium). Issues in sites like youtube, twitch, and jellyfin.
Took a wild guess and installed
libva-mesa-driver (I have an AMD GPU, based on this comment) and
libva-vpdau-driver, as well as the 32 bit counterparts from multilib. Rebooted and things seemed to have been resolved.
Thought this might be useful for anyone with the same problem as me in the future.