IDK. Sway is my daily driver. I just checked Firefox, and the screenshot tool works as expected (including clipboard). So unless GP is talking about capturing non-Firefox windows with that tool, I do not have that issue.

This Firefox instance is running on native Wayland. The only issue I have with it is sometimes the coordinates for the context menu are wrong.

But yeah, there might be compat issues, if some protocols are required for stuff. But Wayland itself is the baseline: you'll always be able to draw windows and interact with them.

What's left to extra protocols isn't guaranteed to work: control of the compositor with a client, for instance (color correction, virtual keyboard, screenshots, window placement, screen geometry, window decorations, etc.) is completely up to the compositor (and the protocols it can speak with the client). So is other stuff, like graphics tablet input (with pressure sensitivity, tile, etc), minimizing windows, window miniatures as used for KDE's taskbar as well, I think.

But then, it's not like everything worked flawlessly everywhere on X either :) And as long as the baseline is solid, we can build on it.