Since this old thread popped up I can add some info. Support for Apple Music and Tidal are up to those companies to add. This is not something Garmin creates. Spotify is an app from Spotify. Amazon Music is created by Amazon. Deezer is created by Deezer.
You should ask Apple and Tidal to create apps for Garmin.
We know that there is no Tidal Garmin integration. But don't worry. Garmin Watch allows users to add local music for playback. So, we can import local Tidal audio into Garmin Watch for use. However, obtaining local tidal music requires third-party tools. This is because Tidal music files are protected. You can use the Tunelf Tidal Music Converter to obtain Garmin Watch's Tidal as a local file on your computer. Then you can transfer Tidal music to the Garmin watch for playback.
