I don’t think Sonos will officially support any iOS beta software until sometime after it is formally released to production - not least because the Apple beta software may change before its general release.

Developers can waste a lot of time attempting to keep up with Apple betas, only to get burned by a late change that breaks something. Of course the Apple Apps didn’t break and this contributes to folklore that Apple is the most competent developer. Many developers, rather than incrementally wasting their own new feature development time, wait until the Apple release before responding to Apple changes.

Though it is not mentioned on https://support.sonos.com/en/article/sonos-app-requirements, I do not think Sonos supports beta version of OS’s.