system/modules/wm.nix

{ ... }:
{
  services.desktopManager.plasma6.enable = false;

  services.xserver = {
    enable = false;
    xkb = {
      layout = "us";
      variant = "";
    };
    videoDrivers = [ "nvidia" ];
  };

  services.displayManager.sddm = {
    enable = true;
    autoNumlock = true;
    enableHidpi = true;
    settings = {
      X11 = {
        MinimumVT = 7;
        DisplayCommand="/etc/sddm/Xsetup";
      };
    };
    wayland = {
      enable = true;
    };
  };
}