My Nixos gamescope setup.

configuration.nix

# Edit this configuration file to define what should be installed on
# your system. Help is available in the configuration.nix(5) man page, on
# https://search.nixos.org/options and in the NixOS manual (`nixos-help`).

{ config, lib, pkgs, ... }:

{
  imports =
    [ # Include the results of the hardware scan.
      ./hardware-configuration.nix
    ];

  # Use the systemd-boot EFI boot loader.
  boot.loader.systemd-boot.enable = true;
  boot.loader.efi.canTouchEfiVariables = true;
  nixpkgs.config.allowUnfree = true; 

  networking.hostName = "nixoshtpc"; # Define your hostname.


  networking.networkmanager.enable = true;


  # Set your time zone.
  # time.timeZone = "Europe/Amsterdam";

  # Configure network proxy if necessary
  # networking.proxy.default = "http://user:password@proxy:port/";
  # networking.proxy.noProxy = "127.0.0.1,localhost,internal.domain";

  # Select internationalisation properties.
  # i18n.defaultLocale = "en_US.UTF-8";
  # console = {
  #   font = "Lat2-Terminus16";
  #   keyMap = "us";
  #   useXkbConfig = true; # use xkb.options in tty.
  # };

  # Enable the X11 windowing system.
  # services.xserver.enable = true;

# SteamOS stuff

    nix = {
   package = pkgs.nixFlakes;
   extraOptions = lib.optionalString (config.nix.package == pkgs.nixFlakes)
     "experimental-features = nix-command flakes";
  };

  services.xserver.videoDrivers = [ "amdgpu" ];
  services.xserver.displayManager.lightdm.enable = false; 
  services.xserver.displayManager.gdm.enable = true; 
  services.xserver.enable = true; 
  programs.steam.gamescopeSession.enable = true; 
  programs.gamescope.enable = true; 
 # services.xserver.desktopManager.gnome.enable = true;

  services.xserver.displayManager.autoLogin.enable = true; 
  services.xserver.displayManager.autoLogin.user = "tombert"; 

  systemd.services."getty@tty1".enable = false; 
  systemd.services."autovt@tty1".enable = false; 

  programs.steam = {
      enable = true; 
  };

  # Configure keymap in X11
  # services.xserver.xkb.layout = "us";
  # services.xserver.xkb.options = "eurosign:e,caps:escape";

  # Enable CUPS to print documents.
  # services.printing.enable = true;

  # Enable sound.
  # hardware.pulseaudio.enable = true;
  # OR
  services.pipewire = {
     enable = true;
     pulse.enable = true;
  };

  # Enable touchpad support (enabled default in most desktopManager).
  # services.libinput.enable = true;

  # Define a user account. Don't forget to set a password with ‘passwd’.
  users.users.tombert = {
     isNormalUser = true;
     initialPassword = "pw123"; 
     extraGroups = [ "wheel" "networkmanager"]; # Enable ‘sudo’ for the user.
     packages = with pkgs; [
       tree
       neovim
     ];
  };

  # List packages installed in system profile. To search, run:
  # $ nix search wget
  environment.systemPackages = with pkgs; [
     vim # Do not forget to add an editor to edit configuration.nix! The Nano editor is also installed by default.
     wget
     google-chrome
     chromium
     neovim
     nss
   ];





  # Enable the OpenSSH daemon.
  services.openssh.enable = true;

  system.stateVersion = "24.05"; # Did you read the comment?

}