You can stream YouTube Music through the Sonos app. Follow these instructions to add YouTube Music to the Sonos app: 

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

Is your question about music on YouTube or YouTube Music? 

My question is about YouTube or YouTube Music. But that does not work for both, from an Android device. (Also please note I do not have a paid subscription to those apps.)

My understanding is that only works from Apple air play.. : /

Youtube Music is one of the Music services that can be added to Sonos, see the link by GuitarSuperstar.  I use it and it work well.

You Tube video from Android is tougher.  However if you are doing so from an Arc can you not use the Smart service on the TV or any attached set top box?  In the UK I can use the Youtub app on my Panasonic TV, the App on the Sky box, or my preferred which is the Youtube app on the Apple tv/Amazon Fire stick.

That does not work.. I have added Youtube Music on the Sonos library. But when I click on it, there is nothing. I ve authorized the app, nut nothing happens.. (I do not want to do it with the TV..)

In order to stream from YouTube music, you need to have a Premium account or a Free account with your own music uploaded.  It also must be available in your region.  See:

https://support.sonos.com/en-us/services/youtube-music