[gf000]

Which native framework?

Even in a "post-vibe code" era I wouldn't want to create multiple versions of the same app, and none of the "platform-native" GUI toolkits run on everything.

SwiftUI is apple-only, gtk has pretty bad compatibility on non-linux, qt is decent but requires C++ or python, and even so still not much for mobile. Don't even get started on "Windows frameworks", because as I write this sentence they may have left a new one in the ditch.

Flutter may be the closest, but why didn't they go with e.g. Java instead of a new language?

So yeah, if you want a truly universal UI then web is your best bet.