You already have it. Host your own damn mp3s and RSS file on your own site. Here's a tool, that's 100% v4v, meaning you get to choose the split, all the way down to 0%. It builds the RSS for you. All you have to do is paste the links to your artwork and mp3 files. Host that shit on a blossom server, put the feed on github, good to go, doesn't cost a dime. Distributing your music shouldn't cost you 10%.

https://musicsideproject.com/