Latest Firefox trunk with applied Wayland patches from Mozilla bugzilla [1].

Build with "--enable-default-toolkit=cairo-gtk3-wayland" and run as $GDK_BACKEND=wayland ./firefox.

There's also compiled version available as flatpak [2] at Fedora hosted site.

[1] https://bugzilla.mozilla.org/show_bug.cgi?id=6351342
[2] https://firefox-flatpak.mojefedora.cz/