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 = {
@@ -74,6 +80,8 @@
                     };
                 };
         
+                networking.nameservers = [ "127.0.0.1@5335" ];
+                
                 system.stateVersion = "24.05";
             };
         };