I recently bought some smart devices and I've been playing around with plugging/unplugging my cable internet connection to see what continues to work and what doesn't. It's nice to have evidence of Matter-over-Wi-Fi (not just Thread) continuing to work even when there's no internet connection, though this may vary depending on the hub in use. TP-Link Tapo devices can also be controlled over Wi-Fi without internet, separately from Matter. Even if you ignore the privacy ramifications, it's pretty magical when tapping a button on your phone toggles a light with nearly zero delay.
