Yes, WiiM is compatible with YouTube Music.
YouTube Music is now fully integrated into the WiiM Home app, giving you seamless access to your favorite songs and playlists directly on your WiiM devices. Simply sign in with your YouTube Music Premium account to browse, search, and play your playlists, albums, and tracks right from the WiiM Home app. For details, see YouTube Music Service Now Available in the WiiM Home App.
In addition, you can also stream music from the YouTube Music app via Bluetooth, AirPlay, and Google Cast to your WiiM devices. For details, see How to Stream YouTube Music to Your WiiM Devices.