You can using Realtime Database. But you need to do custom code. As you know, FlutterFlow can do everything with custom coding or after downloading the code.

To use the Realtime Database, there is nothing much from the way how custom code goes.

Add the realtime database package.
Initialize it. Don't forget to initialize !!
And simply use it.

Note that, you don't need to initialize in Android or iOS mode. But you need to initialize in the Web mode.

The initialization means, use the Database URL to the existing Firebase.

This is what my code goes. You may have an idea from it

\n  /// Returns the firebase database\n  ///\n  /// * It is important to use this method to get the database reference.\n  /// * Do not use `FirebaseDatabase.instance` directly.\n  ///\n  /// If it's web, then it requires the databaseURL.\n  ///\n  /// For mobile app, the databaseURL is automatically set in the google\n  /// service files by the FlutterFlow framework.\n  FirebaseDatabase get database {\n    if (kIsWeb) {\n      databaseURL ??= FFLibraryValues().databaseURL;\n      if (databaseURL == null) {\n        throw Exception('SuperLibrary.databaseURL is null');\n      }\n\n      _database ??= FirebaseDatabase.instanceFor(\n        app: Firebase.app(),\n        databaseURL: databaseURL,\n      );\n\n      return _database!;\n    }\n    return FirebaseDatabase.instance;\n  }

How to connect realtime database firebase in flutterflow