nixos/system/gamescope.nix

{...}: {
  imports = [./desktop.nix ./games.nix];
  services = {
    greetd.settings = let
      command = ''
        gamescope\
          --nested-refresh 60\
          --scaler auto --filter fsr --fsr-sharpness 10\
          --hide-cursor-delay 5 --steam -- steam -gamepadui
      '';
    in {
      default_session = {inherit command;};
      initial_session = {inherit command;};
    };
  };
  programs.steam.gamescopeSession.enable = true;
}