Sonos recently announced that older Sonos devices would no longer be receiving software updates after May 2020. This included security fixes, bug fixes, and new feature updates. New features would only be available on newer devices. CEO Patrick Spence has apologized for the original plan and stated that they will continue to offer security updates and bug fixes to legacy equipment. They are working on a way to allow new devices to continue to receive software updates when used on the same system as older discontinued products. More details about the plan to have modern and legacy products working together will be released in the coming weeks.
Source: https://www.bleepingcomputer.com/news/technology/sonos-backtracks-legacy-devices-will-get-updates-after-may/