https://www.theverge.com/2018/6/6/17434294/airplay-2-sonos-speakers-in-july

Sonos just announced that AirPlay 2 is coming to “newer” Sonos speakers in July. Unlike using Apple Music on the HomePod, it will stream music from your phone instead of directly over the internet. However, unlike the HomePod, you will be able to control some of the AirPlay 2 music with Alexa. You can launch music on your iOS device in all the normal ways, including Siri.

Essentially, Sonos’ software system is able to be aware of what is playing on your speakers, no matter the source. It’s a clever way to make AirPlay 2 a little more useful. Once the music is playing via AirPlay 2, you can use Alexa to pause, go to the next track, and even ask what’s playing.