https://www.reddit.com/r/homeassistant/comments/895iw6/my_home_assistant_setup_rpi_3b_docker_compose/

docker-compose.yaml

version: '2.1'
services:
  grafana:
    container_name: grafana
    image: proxx/grafana-armv7
    user: "1000"
    ports:
      - 3000:3000
    volumes:
      - /opt/grafana:/etc/grafana:rw
      - /opt/grafana:/var/lib/grafana:rw
      - /etc/timezone:/etc/timezone:ro
    restart: on-failure
    depends_on:
      influxdb:
        condition: service_healthy

  influxdb:
    container_name: influxdb
    image: influxdb
    ports:
      - 8086:8086
    volumes:
      - /opt/influxdb/influxdb.conf:/etc/influxdb/influxdb.conf:ro
      - /opt/influxdb:/var/lib/influxdb
    restart: on-failure
    healthcheck:
      test: ["CMD", "curl", "-sI", "http://127.0.0.1:8086/ping"]
      interval: 30s
      timeout: 1s
      retries: 24
      
  homeassistant:
    container_name: homeassistant
    image: homeassistant/raspberrypi3-homeassistant:0.87.1
    network_mode: "host"
    volumes:
      - /opt/homeassistant:/config
      - /etc/localtime:/etc/localtime:ro
      - /etc/letsencrypt:/etc/letsencrypt:ro
    devices:
      - /dev/ttyUSB0:/dev/ttyUSB0:rwm
      - /dev/ttyUSB1:/dev/ttyUSB1:rwm
    restart: on-failure
    depends_on:
      influxdb:
        condition: service_healthy
      mosquitto:
        condition: service_started
    healthcheck:
      test: ["CMD", "curl", "-f", "http://127.0.0.1:8123"]
      interval: 30s
      timeout: 10s
      retries: 6

  node-red:
    container_name: node-red
    image: nodered/node-red-docker:rpi-v8
    ports:
      - 1880:1880
    volumes:
      - /opt/node-red:/data
      - /etc/localtime:/etc/localtime:ro
      - /etc/timezone:/etc/timezone:ro
    restart: "no" # because the exit code(s) are wrong
    depends_on:
      mosquitto:
        condition: service_started
      mqtt-bridge:
        condition: service_started
      homeassistant:
        condition: service_healthy
    healthcheck:
      test: ["CMD", "curl", "-f", "http://127.0.0.1:1880"]
      interval: 30s
      timeout: 10s
      retries: 5

  mosquitto:
    container_name: mosquitto
    image: eclipse-mosquitto
    user: "1000:1000"
    ports:
      - 1883:1883
    volumes:
      - /etc/localtime:/etc/localtime:ro
      - /opt/mosquitto:/mosquitto/config:ro
      - /opt/mosquitto:/mosquitto/data
    restart: on-failure

  mqtt-bridge:
    container_name: mqtt-bridge
    build:
      context: https://github.com/stjohnjohnson/smartthings-mqtt-bridge.git
      dockerfile: Dockerfile-rpi
    ports:
      - 8080:8080
    volumes:
      - /opt/mqtt-bridge:/config
    restart: on-failure
    depends_on:
      homeassistant:
        condition: service_healthy

  portainer:
    container_name: portainer
    image: portainer/portainer
    ports:
      - 9000:9000
    volumes:
      - /opt/portainer:/data:rw
      - /var/run/docker.sock:/var/run/docker.sock
    restart: "no" # because the exit code(s) are wrong

  organizr:
    container_name: organizr
    image: lsioarmhf/organizr
    ports:
      - 80:80
      - 443:443
    volumes:
      - /opt/organizr:/config:rw
      - /etc/letsencrypt:/etc/letsencrypt:ro
    environment:
      - PGID=1000
      - PUID=1000
    restart: on-failure
    healthcheck:
      test: ["CMD", "curl", "-f", "http://127.0.0.1"]
      interval: 30s
      timeout: 10s
      retries: 5

  dockermon:
    container_name: dockermon
    image: tribunex/ha-dockermon-pi
    ports:
      - 8126:8126
    volumes:
      - /var/run/docker.sock:/var/run/docker.sock
      - /opt/dockermon:/config
    restart: on-failure

Note that I did not say "shut down the old mosquitto instance". Even if you stop it, a service that is still ENABLED will start right back up when you reboot.

apt search mosquitto ...look for items that say [installed] and uninstall them.

To be more clear: mosquitto that you have installed DIRECTLY on the system is interfering with the mosquitto that you're trying to run in docker.

Thanks a lot!
I did the search, deleted the instance running directly on my Pi and rebooted - everything worked like a charm!

I really appriciate your help!
The guide you made - aswell as another RPi4 orientated guide (refering to yours) are the two single best entry angle, when a person have no knowledge about docker. Great work.

Wounder how this instance got installed on the pi in the first place - where i fucked up.....