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.
Don’t know about the OP, but I only have one version installed. If I don’t have it open, a single icon shows on the task bar. If I press that icon, FF opens and a second icon shows up, that represents only the opened FF, while the original icon remains.