Currently, it seems like the Google Home app cannot control any devices without internet. I tested disconnecting separating my routers (LAN) from Internet (WAN), and the Home app can't do anything. Even devices that support Matter and are connected locally through thread. For example, I have a few Nanoleaf Matter bulbs connected to a Nest Hub through thread. When the internet is down the Google Home app cannot control these devices, but the Nanoleaf app can still access the Nest Hub's fabric through thread. (Phone Wi-FI -> Router Wi-Fi -> Nest Hub Wi-Fi -> Nest Hub Thread -> Nanoleaf Bulb Thread). I don't understand why the Google Home app requires internet.
Similarly the Philips Hue App can still control lights without internet. (I understand this is currently not through Matter + Thread, but Zigbee.) Philips will be updating their bridge to Matter later.
I expect the Google Home app to gain offline support to allow controlling devices locally through Matter (Wi-Fi, Ethernet, Thread, etc.) even without Internet (WAN). I haven't heard anything about whether this functionality is planned or not in any blog post, articles from a tech site, etc. If someone knows whether this is planned or not, please post here! Thank you.
(I am currently running Google Home App v3.2.1.7 with Public Preview enabled.)
