I actually recommend this app – SongShift Review

Not perfect, but dear god am I so glad this app exists and works as well as it does. I’ve switched back and forth between Spotify and Apple Music like five times now, and this app has been crucial in allowing that. It’s one of the few apps I actually recommend to people irl. It’s def worth getting the Pro version or whatever it’s called, it lets you do your whole library at once. Otherwise you gotta do it one playlist at a time interspersed with random ads. Keep in mind though, it skips a handful of tracks when importing/exporting, it’s not perfect, so make sure to double check and cross reference your playlists when you’re done with a transfer if absolute accuracy is important to you.
Review by WebbyUrchin on SongShift.