Xlibre (the only current actively developed implementation of a X11 server) has a new extension - XNamespace to address some challenges as well.

https://github.com/X11Libre/xserver/blob/master/doc/Xnamespa...

Not the only one, there's also a new one (written in zig) I've forgot the name of.

edit: phoenix was the name: https://github.com/external-mirrors/phoenix#phoenix