just wanted to share what I learned from the support about Airplay 2 and Sonos groups.
When trying to cast something to a Sonos One SL speaker using Airplay 2 (for instance from Apple Music) to a group defined in the Sonos app, Airplay 2 will not display the group, only individual speakers.
Apparently this is working as designed which to me is a deficiency. Using the Sonos iOS app it is possible to cast to a group. It should be possible to do the same regardless of which app is being used.
According to the support my request has been forwarded as a request for improvement. One can only hope this makes it into production in a not to far future.