This is what I do but with qbittorrent and ProtonVPN. Just put the port details in the gluetun section and in the qbittorrent section put in network_mode: “service:gluetun”. Works just fine so far for me.

https://github.com/qdm12/gluetun/wiki/Connect-a-container-to-gluetun

---
version: "2.1"
services:
  gluetun:
    image: qmcgaw/gluetun
    container_name: gluetun
    cap_add:
      - NET_ADMIN
    devices:
      - /dev/net/tun:/dev/net/tun
    network_mode: bridge
    ports:
      - 8081:8000/tcp # http control
      - 8888:8888/tcp # HTTP proxy
      - 8080:8080/tcp # qBittorrent
      - 9117:9117/tcp # Jackett
    volumes:
      - /docker/gluetun:/gluetun
    environment:
      - VPN_SERVICE_PROVIDER=protonvpn
      - TZ=Europe/London
      - SERVER_COUNTRIES=Netherlands
      - OPENVPN_USER=USERNAME
      - OPENVPN_PASSWORD=PASSWORD
      - HTTPPROXY=on
      - HTTPPROXY_STEALTH=on
      - HTTPPROXY_USER=username
      - HTTPPROXY_PASSWORD=password
    restart: always

  qbittorrent:
    image: ghcr.io/linuxserver/qbittorrent
    container_name: qbittorrent
    network_mode: "service:gluetun"
    environment:
      - PUID=1000
      - PGID=100
      - TZ=Europe/London
      - WEBUI_PORT=8080
      - DOCKER_MODS=arafatamim/linuxserver-io-mod-vuetorrent
    volumes:
      - /docker/qbittorrent:/config
      - /srv/mergerfs/downloads/torrents:/downloads
    restart: always