Sync app for Android. I’ve not used it, it says it’s chiefly for managing files synced from desktop. But it seems to imply you can add files in Android and they’ll get synched to proton drive? Perhaps try it out
Failing that the are definitely sync apps for Windows / Mac so you may end up having to move your music there first?
https://proton.me/support/access-synced-folders-android
Sync app for Android. I’ve not used it, it says it’s chiefly for managing files synced from desktop. But it seems to imply you can add files in Android and they’ll get synched to proton drive? Perhaps try it out
Failing that the are definitely sync apps for Windows / Mac so you may end up having to move your music there first?