According to Phoronix it's in:
https://www.phoronix.com/scan.php?page=news_item&px=Firefox-...
plan to be on ff 76
https://www.phoronix.com/scan.php?page=news_item&px=Firefox-...
Although probably not enabled by default.
According to https://wiki.archlinux.org/index.php/Firefox#Wayland, if you want to see whether you're using the Wayland version of Firefox, go to about:support and look next to "Window Protocol". Wayland can be enabled at runtime using an environment variable: `MOZ_ENABLE_WAYLAND=1 firefox`.
I just updated to Firefox 75 and it's still using x11. If I opt in to using Wayland, it works, but annoyingly I can't detach a tab by dragging it off of the window. So it looks like Wayland support is not quite there yet.
Re:Firefox 75: Ambitions for April
by mauricedenassau on Tuesday April 07, 2020 @01:18PM
(#22805260)
I second this, since I switched to wayland, I noticed many weird graphical issues with Firefox, hoping this release will fix them.
It's a bit unclear if it hasn't made it to the final release, or if it's just a matter of the Linux userbase being too small for them to announce Linux-specific changes.