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.
flatpak isn't the same because you only have to learn one packaging format and can distribute to virtually any system out there. I really don't see why you'd also package for every distro individually then. Installing flatpak isn't that hard, it not being "the defacto standard" shouldn't be an issue.
If the system supports flatpak. Yes.
So basically the entire Linux desktop then.