Sonos publish an API for MSP’s to link their music services to the Sonos ecosystem. Apple have done this for their general Music service, but it’s down to Apple mainly (and Sonos, perhaps to a lesser extent) to implement their new classical service.

I’m sure Sonos will acknowledge your post here as a ‘feature request’, but it will also pay you, as an Apple customer, to canvass Apple to add their new Classical service to Sonos too. So don’t forget to contact Apple and let them know aswell.