try

system-config/services/containers/pihole/default.nix

@@ -59,6 +59,12 @@
                             }
                         ];
 
+                        /*settings = {
+                            misc.dnsmasq_lines = [
+                                "no-resolv"
+                                "server=127.0.0.1@5335"
+                            ];
+                        };*/
                     };
 
                     unbound = {
@@ -73,6 +79,8 @@
                         };
                     };
                 };
+        
+                networking.nameservers = [ "127.0.0.1@5335" ];
                 
                 system.stateVersion = "24.05";
             };