Without Wi-Fi or internet

Your wall switches always work, even without Wi-Fi or internet. The module needs the internet only for the app and voice control. It does not work over your local network alone.

During an internet outage the module shows as offline in the app. App control comes back by itself when the internet returns.

You don't need a hub. Each module has its own Wi-Fi and connects straight to your home router. It can also connect to a mobile hotspot.