Flutter is starting to look real nice as the host environment for visual programming environment experiments, check out iRobot's block based tool, implemented in flutter https://edu.irobot.com/the-latest/building-a-coding-experience-for-all

As someone who doesn't know much about Flutter, I'm curious what about it looks appealing to you as a "host environment for visual programming environment experiments". The article you linked to includes three desiderata that Flutter supposedly fulfills (screenshotted below). But other than the cross-platform stuff – which matters to some, but certainly not all, programming experiments – they seem like criteria Typescript + HTML5 would accommodate. Or not, if there are ways Flutter goes beyond that I don't know about! But I haven't seen a specific articulation of how that might be. (A natural question this is raising for me is, what WOULD I want out of a host environment? That's a good, separate, question.)

@Joshua Horowitz Native app on multiple platforms (with wasm in the browser) plus an extremely sophisticated graphics library. It's a great reduction of the barrier to making very performant cross-platform GUIs, at least in theory.

@Joshua Horowitz agreeing with @Jack Rusher - you can expect it to be faster with relatively similar primitives as react+TS, minus the DOM weirdness. Its far from perfect though - JSX remains more ergonomic than their weird constructor composition, packages kinda suck, and text support is very strange (since it's all virtual)

Random opinions: Flutter is super appealing if you don’t want to spend years learning the insanity of browser dev. That’s why I originally started with Dart, but ended up having to bite the bullet. Also if you need silky animation (React Native maybe is OK too, don’t know). If you want to develop a UI programming environment, Flutter has a much simpler model to translate into. But browser dev has like 100x community size, which matters a lot.