services:
  qbittorrent:
    image: lscr.io/linuxserver/qbittorrent
    container_name: qbittorrent
    environment:
      - PUID=888
      - PGID=888
      - TZ=Australia/Perth
      - WEBUI_PORT=8080
    volumes:
      - ./config:/config
      - /srv/downloads:/downloads
    restart: unless-stopped
    network_mode: "container:wg_out"

this is my compose.yml for a qbittorrent instance.

the part you’re interested in is the final line. There’s another container with the wireguard instance called “wg_out”. This network mode attaches this qbittorrent container to that wireguard container’s network stack.