I want to configure and run DarkMX on a Debian Bookworm server without a video card or GUI. I would log in via SSH to configure it.

Is there a API for talking to DarkMX? Is there a way to disable the GUI rendering so it doesn't look for video server and crash?

Any ideas would be great!

There's no API for talking to the program.

The best you could do would be to use Xvfb or Xvnc and then just remote in over VNC.  I've done this on cheap VPS accounts and it works great.