Adding GeneratedPluginRegistrant.registerWith(flutterEngine); to MainActivity.kt did work for me.

import io.flutter.plugins.GeneratedPluginRegistrant

//...

override fun configureFlutterEngine(flutterEngine: FlutterEngine) {
   super.configureFlutterEngine(flutterEngine)
   GeneratedPluginRegistrant.registerWith(flutterEngine);
   configureChannels(flutterEngine)
}

Sousce:
https://github.com/firebase/flutterfire/issues/9113#issuecomment-1188429009