@colinstu Gnome's fractional scaling support is enabled (because it handles moving applications between my 4K and my 1080p display better), but I use 200% and 100% respectively. This setup has worked fine for years and Firefox only broke after the latest update.
My distro is EndeavourOS. I'm pretty sure it installs XWayland by default, so my system was never pure Wayland.
Since it looks and performs fine with XWayland now, I'm happy to leave things alone until the problem is resolved.