Excellent article! Many articles from others tend to be too abstract to be useful. Providing working code makes the subject much more approachable. Well done.

I currently write flutter apps on a mac and I am only using the Material classes. Your article now has me thinking about how do I apply this to an application. There seems to be a need for an entire set of factory classes for many of these controls (Buttons, dialogs and anything else that varies between platforms).