Wayland is viable on FreeBSD, at least. It is very much not “Linux-only”.
https://wiki.freebsd.org/Graphics/Wayland
> While Wayland isn't ready for general use.
I can't readily find anything to indicate that this claim is out of date. I am aware that Wayland has been ported, but I have not heard of it being widely used, or being "production ready" as per se.