this problem is still not fixed in 6.1 my system go to suspend even though I turned it to never. but I will try "hahacompliance" solution and will see
the suspend & suspend time are working but when you don't want the suspend from the beginning it not work it locked the screen after moment it goes to sleep(suspend) and after login in your opened apps all gone what should I do?
solution: to avoid losing your opened apps after screenlock install dconf-editor from the terminal
sudo apt install dconf-editor
then run it org>gnome>gnome-session turn auto-save-session auto-save-session-one-shot on