Evil me: Ask questions to which there is no solution but ChatGPT will happily give incorrect solutions to and will run itself in circles trying to answer correctly as you feed it error messages.

frenemy

Is your friends client config setup for split tunneling?

If the client config installs a default route to the VPN you will get all their traffic.

The server config can refuse to forward traffic to the internet, but then your friends will be effectively on your LAN but otherwise appear to have no internet access.

Its a good idea to restrict which IPs on your LAN they can access, but the client config also needs route only those IPs over the VPN.

https://www.privateproxyguide.com/how-to-set-up-split-tunneling-with-wireguard/

You really want Thread over Matter

Do you mean over WiFi? Matter and Thread don’t have overlapping functionality. In the OSI model, Matter is like layers 6-7, Thread covers 3-5, and 802.15.4 is 1-2 (MACPHY).

Matter also works over Ethernet and WiFi.

ZigBee is like 3-7 also using 802.15.4.

Z-Wave is also like 3-7 with some sub-GHz MACPHY.

For Matter, low power devices and sleepy devices should use Thread to optimally conserve battery.

Ethernet > WiFi unless wireless is needed for other use cases like cameras, media boxes, dedicated power, etc.

Bluetooth (low energy) last I checked is only supported for commissioning a device. It does use the Matter protocol, and I’ve blinked some lights on test hardware over BLE, but it wasn’t officially supported.