"Flutter is amazingly successful. It's already the leading mobile app development framework" ???
* Number of developers using it on some daily/weekly/monthly, etc. cadence.
* Number of apps published (to iOS, Android, both).
* Number of jobs available using the framework.
* Various subjective desirability metrics from developers survey like the StackOverflow ones.
It's anyone's guess as to which is the best metric or how they should be combined. Also, it's very hard to actually get accurate data on it.
But, according to Statistica at least, yes Flutter really is the most popular mobile app framework as of 2022:
https://www.statista.com/statistics/869224/worldwide-softwar...
It looks like that's based on a developer survey. I don't know more about its methodology.
So 46% of 33% of mobile app developers that aren't building mobile websites use Flutter. That's not bad at all, but hardly supports a claim of being the "leading mobile app development framework" as you're down to ~15% of mobile app developers using it. And only then since mobile web is being excluded, who knows what it'd be if that was included.
People who use Swift/UIKit to make apps may like it, but it's also the default way to make an iOS app, so they don't feel the need to fight a war. That language was handed down from above as the winner of iOS development. Same for Java/Kotlin/native UI libraries on Android.
Unless you want to count them both as Native at 50%?
Flutter: 46% React Native: 35% Unity: 10% Cordova: 10% Ionic: 9% Xamarin: 8%
Just one datapoint, of course - a survey of 26,384 developers.