While i was using Devuan, i ran startx as a normal user (instead of using sudo).
Surprisingly, i was able to get a screen. However, neither the keyboard or mouse would work so i had to reboot.
Fast forward to now, i was very annoyed to see people claiming that you need to have systemd in order to run Xorg without any root rights.
I later discovered it was in fact false, as people were able to do just that before systemd even existed. (back in 2009)
You do need a driver that supports KVM, which nouveau, intel and radeon does. (i heard nvidia's proprietary driver also recently supports KVM)
Also make sure to use libinput for xorg.
It was a simple matter of making a udev script (or using chown on /dev/input*, your choice) and voila, Xorg without any root rights.
It's worth nothing that none of this would work with a window manager. (In fact, i think SDDM still doesn't support rootless xorg !)
So i also had to make it nice and convenient for me to use and i opted for a script in /etc/profile.d which will prompt you if you want to run your window manager. (with xorg of course)
You can give it a try here :https://github.com/gameblabla/xorg-rootless-devuan