Your own music files play now. Library has a Local tab: point it at a folder and everything in it shows up as albums and songs, with the artwork embedded in the files. It plays with no connection at all, since nothing about a local file goes near YouTube. Untagged files are read from their filenames, and a folder with no album tag is treated as one album.
Deleting a file is handled, not discovered. Every scan reports what left the disk, so a song, an album and any shortcut pointing at them disappear as soon as the app notices, instead of failing the next time you press play.
Every artist in the player bar is a link. Clicking Metro Boomin on a Future & Metro Boomin track opens Metro Boomin, matching what the track rows already did.
Listen Together shows the invite you can actually share, rather than a room code that could not be joined with.