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! 🎉
Well, Google takes 15 to 30% off the in-app purchases made through Google Play, so you would probably be giving back Google their own money anyways, plus it would fool many people who might think they’re giving 10€ when actually they’re only giving 8,50€ or 7€ to Wikipedia and the rest to Google.