How to sync your local iTunes library when you’re subscribed to Apple Music
Apple Music is one of the best music streaming options when you have a local library of unreleased songs, live concerts, or remixes. But this method will also allow you to sync hi-fiedlity music such as ALAC to your iPhone.
While not completely obvious, it is possible to sync your local library while also having a cloud-based Apple Music library on your iPhone or iPad.