In case you need a pointer, I had to do this recently too. I’m no docker expert, but this works for me 👌

---
version: '3'
services:
  gluetun:
   image: qmcgaw/gluetun:latest
   hostname: gluetun
   container_name: gluetun
   restart: always
   cap_add:
    - NET_ADMIN
   environment:
      - VPN_SERVICE_PROVIDER=custom
      - VPN_TYPE=wireguard
      - VPN_ENDPOINT_IP=
      - VPN_ENDPOINT_PORT=51820
      - VPN_PORT_FORWARDING=on
      - VPN_PORT_FORWARDING_PROVIDER=protonvpn
      - WIREGUARD_ADDRESSES=
      - WIREGUARD_PUBLIC_KEY=
      - WIREGUARD_PRIVATE_KEY=
   devices:
    - /dev/net/tun:/dev/net/tun
   ports:
    #Proton
    - 34803:34803/udp
    - 80:80
    #Gluetun
    - 8888:8888/tcp # HTTP proxy
    - 8388:8388/tcp # Shadowsocks
    - 8388:8388/udp # Shadowsocks
    - 8000:8000/tcp # HTTP Control Server
    - 8090:8090 # qBittorrent
   volumes:
    - /docker/appdata/gluetun:/gluetun

#QBITORRENT
  qbittorrent:
    image: linuxserver/qbittorrent:latest
    container_name: qbittorrent
    network_mode: service:gluetun
    depends_on:
      gluetun:
        condition: service_healthy
    environment:
      - PUID=1000
      - PGID=1000
      - WEBUI_PORT=8090
    volumes:  
      - /docker/appdata/qbitorrent:/config  
      - /data/torrents:/data/torrents
    restart: always