Besides Funkwhale, I’m not sure there is anything else at the moment (someone please correct me if I’m wrong)

There are radios on Funkwhale, but these are just a random playlist of songs from a set list (like “Piano radio” for example)

Peertube has a livestreaming function that could be used as a radio closer to the actual sense of the word (with someone animating it), but it would take a lot of effort and I haven’t found any radio channels on Peertube. If you have a great idea, go for it and it might take off! 🎉