This is a guide and shell script to run steam through gamescope on a non-logged in Linux system.
Basically you can remotely connect to your Linux system through ssh, start steam without a desktop environment, and the games will run that way only accessible to the remote streaming devices (ie steam deck, steam link, or other paired steam client).
This looks super useful! Would be interesting to see this as a systemd service built into NixOS, so my gaming machine could always have this running without any manual steps.