Its even worse when you force Firefox to use wayland its icon doesn't even show.
Edit: Oh since everyone now is confused; I only have the flatpak version of Firefox installed yet it doesn't use the pinned icon and doesn't even use the firefox icon under wayland at all.
Very simple. Debian Testing is rolling distro and has fairly fresh versions, usually couple of months behind. Debian Unstable has all the bleeding edge stuff, also rolling. Neither is unstable and insecure as most would expect. If you want non-Debian, there's always Arch and Manjaro.