My iOS app plays music from the user's library via MPMusicPlayerController.applicationMusicPlayer. It can either be from Apple Music or manually synced music files.
Is there a way to have that music show up as recently played in the Music app?
Turns out yes, it happens naturally if you launch playback of an album, as in querying the album by a MPMediaEntityPersistentID and giving the resulting MPMediaItemCollection as a queue to the player.
What I was doing though is creating a custom song queue for playback, usually from a given album, and then I'd expect the Music app to show that album as recently played. But the Music app won't pick it up that way.