I have had this issue on other distros as well, and am trying to get to the root of it. I have tried emptying Firefox cache, disabling hardware acceleration, etc, but nothing seems to affect it. After every refresh to make the audio get in sync with video, it begins desyncing again after 10-30 seconds again. Anyone else having the same issue? Is this a driver thing? I can’t even find where to change drivers in EndeavourOS. I would experiment with that, if anyone can give me a hint where to look for that in settings.