Firefox is great and all, but its consistently buggy with its clipboard on Gnome/Wayland for the past year.
At least it's consistent :D
For me it is: I can't copy from the URL-bar to other apps. Inside of firefox works, copying from everywhere else works.
I didn't care to investigate though as I rarely need to do that and I was pretty sure it's my fault for locking it into it's own user namespaces.