Seatd

The Problem Part 2 ended with a gamescope TV session that could be started and stopped independently - but with an immediate new problem: moving the desk mouse moved the cursor in Steam Big Picture on the TV. Keyboard keys navigated Steam menus. This shouldn’t happen. The desk mouse and keyboard are seat0 devices - they are not tagged for seat1 in udev, so seatd should not have given gamescope access to them. The gamescope log confirmed this - there were no “Adding device” messages from libinput. gamescope itself received no input devices through seatd. ...

The Goal Part 1 ended with a working setup and one major limitation: the TV gaming session on seat1 was always-on. To stop it - for GPU passthrough to a Windows VM, or to run Steam on the desk instead - required restarting all of LightDM, which also killed the Sway session on seat0 and lost all open windows. The goal: replace LightDM’s static seat1 management with something that can be stopped and started independently, without touching seat0. ...