How to create a Flutter plugin that works in another Flutter project?
Turns out that not the plugin-adding is the problem!
It is rather my large asset that I have inside the Flutter app that causes the exception.
And it must be more or less a coincidence that my Flutter app crashes from the moment I add the plugin to my app. It was misleading. (I therefore assume that the exception might have happened as well - later when I build-up my Flutter app and add more code. It might be a memory issue of some sort...or you tell me!)
As soon as I remove my large asset (665 MB), the plugin integration works smoothly without any exception.
The question shifts tough to another StackOverflow question: How to integrate a large asset in my Flutter app
And this query can be closed.