I only looked enough into Elm to determine it's not for me. But this relates to the main reason I made that decision: it's explicitly designed to be hard to integrate with javascript.
Integrating React and Elm is hard because they can only communicate via message passing. Synchronous js calls are restricted to packages whitelisted by the Elm compiler.
Same, I never got Elm, I'd want to work as close to JS as possible. I like TypeScript but I likely wouldn't use another compile to JS language, if only based on the npm ecosystem size in general.
Then I heard the horror stories about Elm, and how the creator really hates criticism while simultaneously carving out features in the compiler for his friends, and I decided it wasn't for me.