I haven't really looked, apart from glancing, into flutter yet. Now with desktops and mobile, premise seems interesting. How and does it compare to Qt?
Qt also has a WebAssembly build for QML apps on the web but in my experience it has suffered from some of the same issues reported here about the Flutter WebAssembly runtime.
Edit: One key difference is Flutter seems to do everything with procedural code. QML is based on a declarative DSL plus Javascript.
Incidentally, I was pretty sure that Dart was dead. Turns out it's alive. I'm not sure what it is currently, now that it's statically typed, null safe and all. What are Dart's killer features?
Looks like we're discussing one - flutter?
It's not clear to me that killer features are really a thing for most languages. Sure Haskell has laziness/purity and Rust has ownership.
But what is C++'s "killer feature"? C interop? It used to be OOP but it's not that any more and yet C++ is still massively successful. What is Java's killer feature? GC? C#'s?
I think most languages don't have killer features, they have killer platforms and frameworks. For C, it was Unix. For Java, it was servers and the broad set of libraries. For C# it was WinForms and now Unity. For JS, obviously, the web.