Run two Foundry Virtual Tabletop instances from the same docker-compose file.

docker-compose.yml

---
version: "3.8"

secrets:
  credentials:
    file: credentials.json

services:
  foundry_1:
    image: felddy/foundryvtt:release
    hostname: my_foundry_host_1
    init: true
    restart: "unless-stopped"
    volumes:
      - type: bind
        source: ./data_1
        target: /data
    environment:
      - CONTAINER_CACHE=/data/container_cache
      - FOUNDRY_LICENSE_KEY=1
    secrets:
      - source: credentials
        target: config.json
    ports:
      - target: 30000
        published: 30001
        protocol: tcp
  foundry_2:
    image: felddy/foundryvtt:release
    hostname: my_foundry_host_2
    init: true
    restart: "unless-stopped"
    volumes:
      - type: bind
        source: ./data_2
        target: /data
    environment:
      - CONTAINER_CACHE=/data/container_cache
      - FOUNDRY_LICENSE_KEY=2
    secrets:
      - source: credentials
        target: config.json
    ports:
      - target: 30000
        published: 30002
        protocol: tcp