I hope this hasn't already been posted, I did a search on 'Phoenix' but didn't find any related hits. It's a bit out of date.
linuxiac.com
This one looks like a clean-room rewrite, and not a fork of the existing codebase.
It looks like the efforts to keep X11 current are hotting up. Another option to Xlibre, but of course not written in C. I can't find a freebsd port for it available. Still, it's interesting to see these efforts to keep X alive / modernize it. Also interesting to see a project using Zig to do real work.
Phoenix Emerges as a Modern X Server Written From Scratch in Zig
Phoenix is a new X server written from scratch in Zig, aiming to modernize X11 without relying on Xorg code.
It looks like the efforts to keep X11 current are hotting up. Another option to Xlibre, but of course not written in C. I can't find a freebsd port for it available. Still, it's interesting to see these efforts to keep X alive / modernize it. Also interesting to see a project using Zig to do real work.