Exploring the Flutter ecosystem you will come across something called FlutterFlow. This is basically a WYSIWYG development environment which generates the underlying Flutter content for you. I'm just starting to learn this approach to see how much quicker it will be to develop apps using it verse using just Flutter. There are many online tutorials and videos for this environment which I have just started to view. There are also some very nice Flutter dev courses at Udemy. I am currently looking at two and both do a decent job describing the material. Not yet sure which to recommend but both seem to adequately cover flutter. The document set for Flutter is very comprehensive and located at Flutter Dev. The documents for FlutterFlow are also quite extensive.
There are more platforms but I prefer to have some ability to write code so the no code alternatives are not what I'll choose. Between these two platforms I'm still in the decision phase but I'm leaning towards FlutterFlow. Not because its easier to use but because it seems to have a larger ecosystem behind it and more capability for the types of features that I'll want to build into my apps. However, my final decision on this has not been made.