It's moving

nixos/usbguard.nix

@@ -1,10 +1,14 @@
-{config, ...}: {
+# USBGuard:
+# The following line allow all USB devices until a proper policy is configured.
+# Run `sudo usbguard generate-policy` with your devices plugged in,
+# then set rules = "<output>" and switch implicitPolicyTarget to "block".
+# services.usbguard.implicitPolicyTarget = lib.mkForce "allow";
+{
   services.usbguard = {
     enable = true;
     implicitPolicyTarget = "block";
     IPCAllowedUsers = [
       "root"
-      config.var.username
     ];
   };
 }