That's the biggest problem with pure FRP: people like to talk about it and make libraries for it, but non-trivial game implementations are rare. I am still not sure what is supposed to be a unit of re-usability (like components/systems in ECS) in FRP?
They do have some examples of the engine working in the "guide" pages [1], but I don't really know enough about the technology to be impressed. "It's just a black triangle."