For Zigbee, you need a hub for apps to work because the Zigbee protocol is its own thing. If you are lucky, it is Home Assistant and can use that on local netwo

For Zigbee, you need a hub for apps to work because the Zigbee protocol is its own thing. If you are lucky, it is Home Assistant and can use that on local network. If you aren't using HA, then it is custom hub that talks over the Internet to just that app. Big advantage of Matter/Thread is that don't need a hub with its software. It is IP-based protocol. On Wifi or Bluetooth, your phone talks directly to the devices. On Thread, you need a gateway to translate from Wifi to Thread. Your phone only needs to know about Matter. I don't think Matter devices talk over the Internet, I think they use non-routable IPv6 addresses. You can use HA to control over Internet but that uses the HA app. I don't know what other apps do, probably the same custom thing as with Zigbee. Matter works similarly to HomeKit, with direct access to devices, but Matter adds the low-power Thread. It is also standardized so that could have generic Matter app instead of every device being its own app. And can add support to HA instead of custom Wifi and Bluetooth devices.