Enable X11 forwarding on gandalf

systems/gandalf/default.nix

@@ -34,6 +34,7 @@
   networking.firewall.allowedUDPPorts = [ 9 ];
 
   services.xserver.videoDrivers = ["nvidia"];
+  services.openssh.settings.X11Forwarding = true;
 
   hardware = {
     graphics.enable = true;