Libinput options have been renamed.

services/desktop.nix

@@ -46,10 +46,12 @@ in mkIf (elem "desktop" cfg.services) {
     };
     libinput = {
       enable = true;
-      tapping = true;
-      disableWhileTyping = false;
-      naturalScrolling = false;
-      horizontalScrolling = true;
+      touchpad = {
+        tapping = true;
+        disableWhileTyping = false;
+        naturalScrolling = false;
+        horizontalScrolling = true;
+      };
     };
   };
   machine.pkgsets.python3.pkgs = with pkgs.gitpkgs.python38Packages; [ py3status pytz tzlocal ];