Thanks for the insights. Than I might try RustDesk again, and see if they successfully worked around the wayland shortcomings.

Yeah, screensharing is not optimally either, but at least it is working. I mean I could live with a portal which operates like for example a file chooser, but than it should implement the whole process of choosing a window or a screen without any further interaction necesary in the parent application.

That is also a wayland showstopper for me personally. Does someone know if it is a per se wayland issue or is there “only” the implementation missing (i.e. in plasma wayland for instance)?