Right now we're manually doing this in all of our V2 activities in the example apps:

  @Override
  public void configureFlutterEngine(FlutterEngine flutterEngine) {
    flutterEngine.getPlugins().add(new PluginName());
  }

That's something we don't want to really show as an actual example or tell people to do, because GeneratedPluginRegistrant should ideally automatically call getPlugins().add itself for users.

Currently on stable GeneratedPluginRegistrant always uses the old embedding. There's a PR that's about to land on master that will change it to use the new embedding when it's available, #42684.

Once #42684 lands and rolls to stable the migrated plugins should change their example apps to rely on the Registrant instead of manually adding anything in their activity.