Namely, the Spatial Audio feature is tied to the 15.2 update to the Sonos S2 app. Just update directly from the relevant app stores.
Dolby Atmos for music available on Sonos Era 300 speaker and Sonos Arc and Sonos Beam Gen 2 soundbars
If you are lucky enough to already own a new Sonos Era 300 multiroom speaker (officially available for sale since yesterday March 28), you can therefore immediately enjoy the music titles and albums offered in Dolby Atmos for music ( or Spatial Audio) by the Apple Music audio streaming service. Good news, Dolby Atmos technology for music also concerns other Sonos products, namely the Sonos Arc and Sonos Beam Gen 2 soundbars.