Gamescope, the Valve micro-compositor, is now available in version 3.16.22 via the Debian Trixie backports repository (contrib).

Gamescope runs games in an isolated Wayland environment and provides upscaling options including FSR, NIS, and integer scaling - best known from its use on the Steam Deck.

Wraps your games to give them scaling and fullscreen options. A Wayland compositor that enables you to run a virtual display at a different resolution and view it scaled in a window or fullscreen. Supports FSR, NIS, and integer upscaling.

To install, first enable the backports repository and add contrib to your Components line (e.g. Components: main contrib), then run:

sudo apt install -t trixie-backports gamescope

For setup instructions see the official Debian backports documentation.

Source: Reddit