Currently, Apple Music is not currently natively supported in the WiiM Home app. If we have any updates, we'll post them 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/Pro. Or, you can use Siri to voice control the Apple Music playback on WiiM Mini/Pro.
If you have HomePod or HomePod Mini, you could group WiiM Mini/Pro with these devices for a multi-room music system.