Flutter plugin currently only support adding ApplicationLifeCycleDelegates: https://github.com/flutter/engine/blob/main/shell/platform/darwin/ios/framework/Headers/FlutterPlugin.h#L440

App delegates are not available in app extensions. We need to add scene delegate support for app extensions to use those plugins.

One solution is to add a new method called addSceneLifeCycleDelegate and handle it in a similar way to the current addApplicationLifeCycleDelegate.