Yes, Both linux and mac have x servers running. But different variations of them. There is no problem with Linux at all, it is all customizable and user can be just asked to restart a computer to rewrite x server configs.

But on mac and windows this is a quite different situation.

Yes, XDMX is amazing, but the last time I used it (literally 15 years ago), it required a hand crafted xorg.conf, which is not really practical in 2020 with notebooks and frequently changing settings.

XDMX won't work with Mac OS, thought, except you want to work with X11-only apps (defacto a lightweight "virtual machine" without native mac apps).

15 years is long, even longer in Linux time...

Time is relative to your age, young padawan ;-)

The Xdmx changelog stops 16 years ago: http://dmx.sourceforge.net/ChangeLog , the last update at https://sourceforge.net/projects/dmx/ is 5 yrs ago. It still uses CVS at Sourceforge. The code will certainly still run modern day X11 applications, but probably with poor performance.

I wonder what Wayland can offer in this respect (regarding fancy X11 servers such as Xnest, Xvnc or Xdmx).

Any hope of security, for a start! ;D

The reason the first generation iPads may not work is that it is older than Chrome and other browsers started to adopting WebRTC technology. Deskreen is using WebRTC under the hood. So it will not work.