You can play music to the Arc from the Spotify app because of the Spotify Connect feature. You can play almost any music to the Arc from an iPhone because of AirPlay. YouTube Music on a Google Pixel phone doesn’t have either of these options. So you need to stream YouTube Music directly from the Sonos app on the Google Pixel.

Thanks for the reply. How do I stream music directly from the Sonos app on my pixel?

Download the Sonos app on the Google Pixel and follow these instructions:

https://support.sonos.com/en-us/article/add-a-content-service-to-sonos

Thanks