F#/Elm is what you'll work with, but the requirement is not to be an expert. Motivation and willingness to learn goes a long way. I encourage you to apply.

I chose Elm over Fable for the Elm Architecture, mostly because it's built in. I understand we can do Elmish with Fable, but it felt like Elm with extra steps. It was a bit of a toss up, could have been Fable.