Without seemingly any reason my Laptop (ThinkPad T420) on a reboot or fresh start doesn’t start up. By that I mean it gets to the splash screen showing Ubuntu and the five dots underneath which keep stepping from 1 to 5 but never getting to the log in screen. In the past I have successfully restarted the laptop by repairing grub and broken packages and it has booted to the log in screen. Last night it happened again but this time previous fixes wouldn’t work. I found a forum post that suggested disabling Wayland via:
sudo mount -o remount,rw / # to remount the disk r/w
sudo pico /etc/gdm3/custom.conf # edit this file
Then remove the # on this WaylandEnable=false
I restarted my laptop and all is fine.