I just bought a Pi and set this up a couple of weeks ago. I turned my Pi into a NAS using OMV 6 (Open Media Vault - free), installing docker compose and qbittorrent in OMV, also installed gluetun docker in OMV, and then added my, opened a port in AirVpn, and added the port to gluetun and set the network_mode argument in qbittorrent to my gluetun container. Now qbittorrent only connects to my vpn. OMV has extensive documentation for setting it and docker compose up, and the OMV community forum is extremely active.