I have recently gave a look at Qt after 5 years and it seems lots of things have changed for the better. You get the same hot reload like flutter when modifying GUI using QML (with V-Play you can even hot reload not just on simulator/emulator but on real device). Qt material theme has good look and feel. Sadly iOS theme is a little bit lacking.
C++ is probably not the most productive language to write business logic but on the bright side Qt Company recently started supporting Qt for python (Pyside2) - sadly not on mobile devices for now. However it seems you can use PyQT5 on mobiles nowadays. This would be the best of all worlds IMO: 3 highly popular languages with rich libraries, tools and ecosystem -> C++ for speed critical code, Javascript/QML for UI and layout, Python for business logic and as a glue.
Qt also gives me more confidence that is not going away anytime soon. It survived many years and acquisitions (Trolltech, Nokia, Digia) and have some big clients/users in automobile and open source (KDE).
I will closely follow Flutter thought as well as React Native. The latter one also it seems noticed what a pain is writing all those bridges and looks like they are working on it to fix it with new architecture.