Ubuntu not waking up after suspend or sleep

https://askubuntu.com/questions/1032633/18-04-screen-remains-blank-after-wake-up-from-suspend

It is the buggy nouveau driver again. That’s what solved the issue for me. Edit the file /etc/default/grub (using Vi editor — some users have not been able to save after editing in Vi and have had to use the alternate “Ex” editing mode, which substitutes sudo edit below, then Alt+:w and :x for the save and exit commands).

$ sudoedit /etc/default/grub 

Add nouveau.modeset=0 to the line that says GRUB_CMDLINE_LINUX then press CtrlO to save the file and CtrlX to leave Editor.

Run

$ sudo update-grub

Now reboot.