depends how pure you wanna be :)
haskell is the purest of the listed ones.
I personally would pick clojure since they do amazing stuff and it's not bound to a reduced domain like elm.
you could try elixir, erlang, oCaml, LISP and so on.
But Clojure has an active community, rivaling ruby, and that's not that easy because those guys brought a lot of cool stuff into the developer world.
And you have the whole java world to tap into if needed so it's likely a good choice if you don't wanna be a purist.
but that's ofc just my opinion :) since I'm a polyglot and switch paradigms and styles a lot.