it works :D

modules/hosts/nixos-desktop/nixos-desktop.nix

@@ -0,0 +1,12 @@
+{ inputs, ... }: {
+	flake.modules.nixos.nixos-desktop = {
+		imports =
+			with inputs.self.modules.nixos;
+			with inputs.self.factory;
+			[
+				system-desktop
+				systemd-boot
+				i18n-de
+			];
+	};
+}