Playing with X11 and Mate on the Librem 5 is a lot of fun.
#x11 setup
sudo apt install xinit xorg xterm x2x
#run X11
sudo systemctl stop phosh
sudo xinit -- -masterfd 9 9<>/dev/dri/card1
#connect mouse and keyboard from a workstation
ssh -X librem 'x2x -east -to :0'

#x11 ^^^ + mate:
sudo apt install mate compiz-mate compizconfig-settings-manager