I'm running Catalina 10.15.1 Beta and Music.app 10.1.33, and I have a large library of music from CDs. I can see but can't play this music from my iPhone since it's not available in the cloud.
In the Music -> Preferences I have Library: Sync ticked. In list view I see songs with a cloud with dashed outline. I've left the Music.app running for 24 hours and Activity Monitor shows 2.8MB of Sent Bytes.
How do I make Music.app wake up and send music to the cloud?