DSVPN

DSVPN connects a client to the internet through a server you operate. Its README generates a shared secret key and uses that key in the commands at both ends. You supply the server address and optional port rather than signing in to a hosted management service.

Keep the key available to both endpoints through a controlled transfer. The client explicitly blocks IPv6 to prevent traffic outside the tunnel, so this design does not suit a task that requires native IPv6 connectivity. If the device's DNS resolver is reachable only on its original local network, the guide says that resolver may also need changing after connection.