It's from Apple and it's the endorsed UI framework for native development in their ecosystem (more or less). Flutter is not for native development and Jetpack Compose is the equivalent of SwiftUI for Android.

It's been the shiny new thing in iOS development since it's launch and of course there's a lot of division about in the community (it's good, it's bad, it's the future, it will never be the future, etc.)

There are probably just more users of SwiftUI here than Flutter or Jetpack Compose (I think Apple in general is a bit over-represented on HN).

They’re all about improving dev experience, and after all, there’s a large dev audience here wanting to write less and produce more.

It's Apple. Anything Apple is interesting/relevant to Hackernews.