@Wrewdison I'm trying to use JSPF to make them (im)portable, but I haven't actually checked compatibility with anything yet. And also I just realized the in-browser player doesn't link to the JSON. But here's an example, every playlist should have a playlist.jspf.json file:
https://mixtapes.lmorchard.com/03-wheel-of-the-year/from-the-moor-to-the-crypt/playlist.jspf.json