This default setting (suspend at login) affects me in Pop!os 20.04. When away from home I want to login to my home PC, and it is set to boot at 6am. But that's no use when it suspends :)
This is an easy fix:
It's 20 minutes, and is a result of the defaults in
3.28 changing to comply with European and American power-saving regulations.
there appears to be no way of switching the GDM suspend behaviour off
There's currently no UI for it, but if you append this to
# Automatic suspend
# - Time inactive in seconds before suspending with AC power
# 1200=20 minutes, 0=never
# - What to do after sleep-inactive-ac-timeout
# 'blank', 'suspend', 'shutdown', 'hibernate', 'interactive' or 'nothing'
# - As above but when on battery
then reboot (or run "service gdm3 reload" as root), that should put
the GDM session back to the pre-3.28 behaviour. The values are in
seconds, with 0 meaning never; please adjust as needed.
Note: this still works in Ubuntu 21.10.
Also, if you want the screens to go into suspend mode but you don't want to suspend, set a timeout, and set the type to be 'blank'
For changes to take effect, reboot or
sudo systemctl restart gdm3