The new concepts for me were using immutable classes with the keyword "final", and the whole concept of state management in mobile apps because I've mainly done backend.

I've only used kotlin in the android files for flutter but nothing else.

I'm also not totally objective on that because my Java experience is from a long long time ago, my general feeling is that flutter is less bloated than java.

And I don't want to start a culture war on this, because we all know turbo Pascal is the best.

Now with KMP you can build a desktop/iOS/Android app with single codebase as well.