So the following note has been added to the SONOS support topic Use a NAS drive with Sonos.
Sonos app version 80.0
This setting is not currently available in the Sonos app for iOS or Android, but it will return in a future update.
They are forcing the update, and there's no Music Library option in the system menu anymore.
This is very frustrating. Very sloppy software development. Is complaining to support my only option to get this enabled again?