UnifiedPush is specifications and tools that let the user choose how push notifications are delivered. All in a free and open source way.
Check out the documentation here:
- https://unifiedpush.org/developers/flutter/
- To have Firebase as a fallback, https://unifiedpush.org/developers/embedded_fcm/
- An example app can be found here.
- Architecture derived from https://github.com/bkonyi/FlutterGeofencing