If I may make a recommendation: check out ClojureScript with reagent and re-frame when you feel you've achieved what you set out to in Elm. While Elm nailed the essence of FRP, ClojureScript really nails the experience I was looking for in ways Elm can not.
While it doesn't have the gradual typing and fantastic compiler messages, it is also functional and immutable. But to my view it has all around better tooling, very simple FFI (either reference JS already on the page transparently or pull in JS formally via extern definition files similar to TypeScript typings), optional typing via core.typed, sourcemaps with a native debugger, and a node-like full stack synergy through Clojure but with all the power of the JVM.
You definitely lose some confidence at run time due to the dynamic typing, but on the whole I think the gains far exceed that. At least for me it's a package that is very hard to beat.
While it doesn't have the gradual typing and fantastic compiler messages, it is also functional and immutable. But to my view it has all around better tooling, very simple FFI (either reference JS already on the page transparently or pull in JS formally via extern definition files similar to TypeScript typings), optional typing via core.typed, sourcemaps with a native debugger, and a node-like full stack synergy through Clojure but with all the power of the JVM.
You definitely lose some confidence at run time due to the dynamic typing, but on the whole I think the gains far exceed that. At least for me it's a package that is very hard to beat.