I'm afraid Svelte with typescript will loose some of its charm. Typescript is a little more verbose and explicit, also it cannot be directly executed by the browser (so you need to compile it, yet it is intermingled with HTML at times — there's JSX for that but Svelte kinda wants to NOT go the JSX/ShadowDOM route)

Internally Svelte uses TS though, the author claims to love TS also! It just does not mix very well with Svelte.

Stencil.js and lit-element are better picks in this regard IIRC.

Pretty much as you can see. A lot of people want it. It's not done yet.

Obviously Svelte is a JS to JS transformative compiler - you need to make a TS to JS transformative compiler.

I'm hacking on my next app using TypeScript on the backend (particularly around the data layer) and JS/Svelte on the frontend. I would like TS on Svelte, but the rest of Svelte is compelling enough I'd still use it over older tech like React.

Yeah, I love the concepts, philosophy and the simplicity of Svelte, but sadly I can't consider using it until it has proper TS support.