I like this! I'm not sure what's involved in your beta testing nor do I have any idea what TestFlight is, but I'd like to give it a try.

My purchased music that's actually on my iPhone is somewhat limited (maybe a dozen albums) but I'm always using Spotify and increasingly Apple Music; maybe I'm not quite the user you're targeting at this point.

But I'm very much someone who appreciates albums in whole form and care very much about seeing the artwork/info/etc well, as much as is possible in an app...my main jam is vinyl.

edit: I'd potentially find this even more useful in iPad form, where I could pair it to my stereo and have nice, large graphics.