Samsung Galaxy S20
Either after an app update, or seemingly randomly, Spotify reverts the storage for downloaded music back to internal storage from the SD Card.
I have had the music stored on the SD Card before, so it isn't a permission issue. I can also transfer the music back to the SD Card, but that can be a 50/50 chance on finishing without an error.
The issue is not that the music can't be stored on the SD card is that something is happening that causes it to move back to the internal storage. I'm not 100% sure, but quite sure, it is downloading all the music again each time after an update.
I have tried uninstalling and rebooting the phone to make sure it is a clean install, but this hasn't helped.