There's no mention of any of the promised Wayland improvements (which I'd been looking forward to).
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.
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.
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.