Allow GUI root login on Ubuntu 22.04

sudo passwd
sudo nano /etc/gdm3/custom.conf

Inside the GDM configuration file, we need to add the AllowRoot=true line. After you have made this change, you can save and exit the file.

sudo nano /etc/pam.d/gdm-password

Inside of the PAM authentication daemon file, comment out the following line, which denies root access to the graphical user interface, with a pound sign #. You can save your changes and exit this file when done.

auth   required user != root quiet_success