Popularity of Flutter increases steadily: https://trends.google.pl/trends/explore?cat=31&date=today%20...
Yet Flutter fills an important gap in the market: pure native experiences are slowly dying because native look and feel is increasingly meaningless now that so many apps use non native UI kits. Also, supporting multiple UI teams developing for different platforms is a huge risk for small companies and a lot of hassle even for those teams that can afford it. We need more cross platform stuff but I don't believe Flutter is the solution here because of its architecture, which is a combination of "our way or the highway" and vendor lock in. I'd say there is a big risk of Apple doing something smart with Swift on Android and web. I actually know of a few Android developers using Swift on Android already. This is becoming a thing. Like Kotlin, Swift is perfectly positioned to start targeting cross platform via LLVM. Also WASM is becoming a thing. IMHO, Google needs to make U turn here and rip out whatever it is that prevents Flutter from being driven from Kotlin (jvm and native) and other llvm languages.
All that's missing is a proper cross platform UI toolkit that actually works properly in that ecosystem. Things like QT and GTK are obviously usable in that space but a bit clunky/ugly on mobile.
Popularity does not translate in money nor projects, specially with a niche language designed for doing UIs only, lacking libraries left and right.
I reviewed Flutter but got put off by the levels of abstraction.