Ask HN: Writing tools like CoPilot but for prose?

So GitHub CoPilot is all the rage these days. Sure there are annoying rough edges but there’s no denying it’s useful. (I won’t wade into the licensing issues here).

I’m a bit surprised similar tools for writing normal prose haven’t become popular, or maybe I just missed hearing about them.

Are there any similar (cheap/free) tools for writing normal prose?