javascript-x-server VS wlroots

>barrier has been unmaintained for a long time.

As if not having new features added for 2 years makes it stop working? barrier is perfectly fine on normal linux desktop installs. I actually use synergy 1.x personally which has been "unmaintained" for much, much longer. Except synergy 1.x will compile and run on anything from windows 98 to ubuntu 5 to debian 12. You can't get a waynergy or inputleap to compile on an OS more than 2 years old. And even then, as you say, it's crapshoot if the particular wayland will have libei; many like sway are actively hostile to it and never will: https://github.com/swaywm/wlroots/issues/2378

It looks like they actually patched it to filter those modes out, so presumably it worked out of the box and was considered undesirable: https://github.com/swaywm/wlroots/issues/3038

I haven't experienced any of those. The video game performance hit may be due to vsync, but I don't play games so I haven't noticed.

You can however use tinywl. It is an example Wayland compositor that can't do more than displaying one application.

Sway/wlroots has implemented this, but I can't find any discussion for KDE.

wlroots is archived on github. Is it abandoned? Just saying, that only means they moved git hosts :-D

A lot of compositors are based no the wlroots lirbary. So they are still sharing the development effort and have a common base, its just in the form of a library rather than a display server.

gamescope use wlroots