CachyOS has recently stopped playing H264 videos on some websites after a system update.(on Librewolf and other browsers too). Installing ffmpeg4.4 will fix this.

I avoid Brave cause of their history of shady practices like injecting affiliate links in the URL and crypto bloat. If I may suggest, you may still manually add your login sites to the cookie whitelist in Librewolf(‘Manage Exceptions’ under ‘Cookies & Site Data’) and simply continue using it.