YouTube Music is no longer exclusive to the Samsung Galaxy Watch 4 and Galaxy Watch 4 Classic. Google has only released the app to Wear 4100 and Wear 4100+ smartwatches, but it can also be sideloaded to older smartwatches running Wear OS 2.
https://www.notebookcheck.net/Just-Messages-and-Google-Maps-to-go-YouTube-Music-arrives-on-Wear-OS-2-smartwatches.567442.0.html
Youtube Music is garbage, only for google fans