I'm trying to get my iPhone 12 (running iOS 15) to play music (originally from CDs, not locked to any Apple account) that I synced using iTunes from an older mac. I've seen instructions referring to the (built-in) Music (not Apple Music) app, but the iPhone doesn't have this app installed, I can't find it on the store, and I don't want to subscribe to Apple's service (Apple Music) just to play my own mp3 files on my own phone.
Is this app still possible to find somewhere? Has it been quietly replaced by Apple Music? Is there an official way to play local files?