Microsoft has officially communicated many times, including at BUILD 2019 and .NET Conf, that React Native is for Web developers, and Xamarin for .NET developers.
They aren't one pony trick shop.
Qt didn't not take off for free beer mobile devs, it is doing alright for the kind of corporations that actually buy development tools.
Again we aren't talking about SV HN kind of bubbles here.
And I am betting Flutter won't save Dart, specially with Android team doing JetPack Composer and teaming with JetBrains on Kotlin/Native portability between iOS and Android.
Long term, PWAs with WebGL and WebAssembly will take it all.