So I got back to my server, and here’s what I do:

gluetun settings:

services:
  gluetun:
*snip*
    ports:
*snip*
      - 8090:8090 # port for qbittorrent
*snip*

qbittorrent (in the same compose.yml):

  qbittorrent:
    image: linuxserver/qbittorrent:latest
    container_name: qbittorrent
    environment:
*snip*
      - WEBUI_PORT=8090
*snip*
    network_mode: service:gluetun # run on the vpn network
    depends_on:
      gluetun:
        condition: service_healthy
*snip*

Also, in qbittorrent settings you can bind it to a network device. In my case it’s “tun0.” This same thing can probably be done w/ a docker network in a gluetun container and separate containers that rely on that network being up, but I haven’t looked into it. Right now, I have 2 other services that require VPN, and I’m looking at possibly 1 or 2 more. That’s pretty manageable as a single stack, I think.