I'm developing a mobile application with flutter, everything so far is ok, my app needs to check a web API for some available online courses. The problem is, I want the app to notify me when a new course appear as a result of the API call, but I cannot see a proper way to do this even if I think is very simple, I'm not looking for push notifications, just normal notifications, but I cannot find a way to check the API while the app is not opened.
Reading, the flutter_local_notifications package (https://pub.dev/packages/flutter_local_notifications), is recommended, but this seems only to work while the app is opened, even if the example have a notification schedule for X days or time, is not what I need, I cannot see a proper way to check the API on background as everything I read use Isolates and very complex flutter solutions, or just native code (which sounds no complex for me but too much work for just to show a notification).
There is something I'm missing?, there is a simple way to set a callback to my app to check this API and in a true condition show a notification?, something else to have in mind is that as I'm using APIs I don't really like to use firebase for this, implement firebase just for one notification seems too much for me.
Any hints or help will be really appreciate.