Earlier quoted context omitted.
> Wayland is a protocol. It has nothing to do with multi screen support. You're talking about the compositor you used. The one I use handles multi-screen setups quite well. Which compositor do you use?
I use Wayfire [0], a customizable compositor based on wlroots, the same base as sway. It's quite involved and not absolutely perfect yet, but it has some features I haven't yet seen on other DEs like being able to swipe horizontally on your touchpad to smoothly switch workspaces (following your fingers) and the satisfaction of having it properly configured is pretty high. There have been 3 issues I've had regarding i…
Also, is there a chance your 4K screen has negative coordinates? It is well known that Xwayland does not react if an output has negative coordinates (or at least partly negative coordinates).