There's a closed pull request on the void-packages repository

[WIP] Tracking: xorg-server: update to 21.1.0.
https://github.com/void-linux/void-packages/pull/33812

Description:
In WIP because upstream tarballs are botched: https://gitlab.freedesktop.org/xorg/xserver/-/issues/1240 , waiting for 21.1.1.

Added new dependency libxcvt.

xorg-server-xdmx is gone upstream.