Flutter is winning the race in cross platform development. I have been using Flutter for past few days, and I really like the package on whole, tools and community. Having used Xamarin and Qt in the past, Flutter is a lot easier to learn.
I'm curious, when you refer to Qt, do you mean the QWidget application approach or QML? QML is much more like Flutter (but is indeed somewhat arcane to learn how to work with).
I meant Qml, is much more like Flutter, but I felt the learning curve was steeper than flutter.