Amazon Sidewalk is a shared network. Customers with a "Sidewalk Gateway" are able to contribute a small portion of their internet bandwidth, which is pooled together to create a network that benefits all Sidewalk-enabled devices in a community.
For customers with existing devices (e.g., Alexa) that are Sidewalk capable, an over-the air (OTA) update will connect them to the network—no action is needed. Wait a minute. Everyone is opted in by default? Regulators have ruled that is never a good idea!