Smartthings just updated how they handle Sonos speakers today (10/20/20) and released beta firmware 0.32.12.
Post this update, when I discover my Sonos speakers in the new Smartthings app, and then go to Webcore and try to add those speakers to my Webcore, these new speakers are not showing up in the list of devices with speaker capability to add.
Not sure if this is a fix on the Smartthings side or the Webcore side.