Disconnecting shows "Connection failed" (Linux / NetworkManager)

When disconnecting from a location on a Linux system with NetworkManager installed, a "Connection failed" system notification appears. This is a visual bug only — the VPN connection itself is not affected.

The error occurs because NetworkManager attempts to manage the WireGuard network interfaces created by Defguard. When those interfaces are removed on disconnect, NetworkManager reports a failure.

Fix

Tell NetworkManager to ignore all interfaces created by Defguard. Defguard tunnel interfaces are prefixed with wg by default.

1. Create the config file:

sudo nano /etc/NetworkManager/conf.d/90-defguard.conf

2. Add the following content:

[keyfile]
unmanaged-devices=interface-name:wg*

3. Save and restart NetworkManager:

sudo systemctl restart NetworkManager

The notification will no longer appear after this change.