Same beta here, one step further along. iPhone 15 Pro on iOS 27.2 beta 2 (24B5089g), Xcode 27.2 beta. This exact code was reading the library through MusicDataRequest on iOS 27.0. On 27.2 the on-device library still comes back (159 artists), then every request dies while refreshing the user token: ICError -7101, "Missing requesting bundle identifier for user token request." The account lookup fails too: ICError -7013, "Client is not entitled to access account store," and the DSID never comes back. I haven't called developerToken(options: [.ignoreCache]), so I can't confirm the accounts Code=9, but personalized requests are already dead at the user-token step.