Finally switch to flakes.

nixos/desktop/printing.nix

@@ -0,0 +1,20 @@
+{pkgs, ...}: {
+  # Enable printing
+  services = {
+    printing = {
+      enable = true;
+      drivers = with pkgs; [hplip];
+      webInterface = false;
+    };
+    avahi = {
+      enable = true;
+      nssmdns4 = true;
+      openFirewall = true;
+    };
+  };
+
+  # Install programs system-wide
+  environment.systemPackages = with pkgs; [
+    system-config-printer
+  ];
+}