Currently, Apple Music is not supported in the WiiM Home app. If we have any updates, we'll post it to our WiiM Roadmap.
In the meantime, use AirPlay 2 to stream Apple Music from your Apple device (Mac, iPhone, iPad, Apple TV) to the WiiM Mini. Or, you can use Siri to voice control the Apple Music playback on WiiM Mini. If you have HomePod or HomePod Mini, you could group WiiM Mini with these devices for a multi-room music system.