How can you properly customize the actual visual appearance of a displayed notification, such as adding a genuinely custom sound, a specific image, or genuinely custom action buttons, using local notifications combined with FCM data messages?

For a genuinely more customized notification appearance beyond what FCM's own default basic notification display provides, a genuinely common approach combines sending an FCM data only message together with using the flutter_local_notifications package to actually properly construct and display a genuinely fully customized local notification directly on the device itself, letting you control details such as a genuinely custom notification sound, an attached image, or genuinely custom interactive action buttons that a user can directly tap without even actually needing to fully open the app itself.

await FlutterLocalNotificationsPlugin().show(
  0,
  message.data['title'],
  message.data['body'],
  NotificationDetails(android: AndroidNotificationDetails('channel_id', 'Channel Name')),
);