My use case is starting a game stream from my steamdeck after my pc has locked itself. The game will start but the desktop lock screen/screensaver is visible and you can’t play or do anything.
You need to SSH in as the active user (from another device like your phone or another laptop) and run:
You will get a table output with a list of sessions:
SESSION UID USER SEAT TTY 38 1000 james pts/1 44 1000 james pts/2 5 1000 james seat0 tty2
You want to take the one that has a seat allocated and run unlock against it:
loginctl unlock-session 5
Hopefully this will unlock the screen and your steamdeck screen will show the application you’re trying to use.