@spacemanspiffy@purism Firefox isn't that smooth yet. It defaults to GPU accel being off and you can only force the old OpenGL compositor on - no WebRender yet.
However, I'd expect it to become just as smooth once etnaviv and WebRender start to play well with each other :)
@spacemanspiffy@purism Also, recent dmabuf improvements in Firefox on Wayland should have a positive impact - but I've tested only the ESR version so far which doesn't have those.