How to transfer playlists from iPhone to Mac without losing data, including playlists and 3rd party music?

From what I understand, the Sync Library "feature" with Apple Music will only synchronize music that you've purchased from Apple. This is a problem for many people, such as myself, where I purchase music from many sources -- I will often load songs onto my iPhone using another app so I have it on the go. But, if you're not actively synchronizing iOS with your Mac, you will end up losing playlists and content. Not good.

As far as I can tell, to remedy this, I cannot back up the Music library from iOS separately, as it's locked down. Other programs that perform backups of the device are also locked out of backing up Music (why?).

I've been burned by this issue before, where I've lost music and playlists.

Given that I will be getting a new iPhone shortly (next week!), I want to ask the Community at-large about any other means they've been able to utilize to preserve content, including Playlists and individual tracks.

Thanks!