You might enjoy F#. It's a lot like OCaml (which others have mentioned) but being part of the .NET ecosystem there are libraries available for pretty much anything you might want to do.
What do you mean by "outside the .NET world"? F# is a .NET language (more specifically a CLR language). That question seems to be like asking "are Erlang and Elixir contenders outside of the BEAM world?" or "is Clojure a contender outside of the JVM world?".
F# being on top of the CLR and .NET is a benefit. It is very easy to install .NET, and it comes with a huge amount of functionality.
If you're asking if the language F# could be ported to another VM, then I'd say yes, but I don't see the point unless that VM offered similar and additional functionality.
You can use F# as if C# didn't exist, if that's what you mean, and by treating .NET and CLR as an implementation detail, which they effectively are.
You are generally right, but Clojure is a bad example, it is quite deliberately a “hosted” language, that can and does have many implementations for different platforms, e.g. ClojureScript.
Yea, that's true. I forgot about that. I did think of Clojure CLR, but I don't get the impression that this is an all that natural or used implementation so I ignored it. ClojureScript is obviously much more used, although it is still a "different" language.
Fable compiles F# to Python, Rust, and Dart now, too, in addition to JS. I haven't tried Dart or Rust, but when I tried compiling its output to Python it was actually quite good!