All logs related to WireGuard VPN are logged in the system messages and can be accessed via the menu "Information > System > Logfiles". Messages with the service identifiers i2n-wg and kernel: wireguard: are relevant for WireGuard.

The public key of the remote site is included with every message. This can be used to match all messages of a connection. You can find an overview of all public keys under "Information > System > VPN".

If a connection has been successfully established, this is logged as in this example:

i2n-wg[2732]: Connection "Headquarter" (C1) is now online with peer 84.151.22.88:800; [wg800: +cO9V6mUY0PlAjB/6qgO2XpRFy3hUBIamIN2Mxk4LmM=]

If a connection changes to the offline status, the log looks like this:

i2n-wg[2732]: Connection "Headquarter" (C1) is now offline; [wg800: +cO9V6mUY0PlAjB/6qgO2XpRFy3hUBIamIN2Mxk4LmM=]