Flutter definitly has a lot of momentum in this space and I expect it would support the kind of WebView/cross-platform functionality we need (especially given the resources you have helpfully linked here). I don’t have any experience with Flutter, but one concern I have had from doing some reading is:
Flutter ships applications with its own rendering engine which directly outputs pixel data to the screen
In general this is maybe not a problem (though I do get Electron vibes from this approach… 
), but I wonder what affect this has on the size of the app binaries? Increasing our app size from 0.5mb to ~50mb would not be good. My other reservation about Flutter is that it would add the Dart stack to the list of things CHT devs have to work with. (Maybe this is not a huge deal since it would actually be replacing the Java stack and we don’t have a huge depth of experience there anyway…). But, I still feel like I would want to have a clear understanding of the benefits of Flutter over something like Capacitor which seems much more “native” to the NodeJS ecosystem (for better or worse… 
). All of this seems like a great topic for further discussion during a CHT Dev Hour!