Nextcloud + Collabora + Traefik: Could not establish connection to the Collabora Online server.

I create a Docker-Compose file like this, and when I connect Nextcloud with Collabora using Traefik Proxy, it errors. Has anyone encountered this issue before? Help me please;c

My docker-compose file:

services:
  traefik:
    build:
      context: ./traefik
      dockerfile: Dockerfile
    container_name: traefik
    command:
      - "--global.checknewversion=false"
      - "--global.sendanonymoususage=false"
      - "--log=true"
      - "--log.level=INFO"
      - "--entrypoints.http=true"
      - "--entrypoints.http.address=:80"
      - "--entrypoints.http.http.redirections.entrypoint.to=https"
      - "--entrypoints.http.http.redirections.entrypoint.scheme=https"
      - "--entrypoints.https=true"
      - "--entrypoints.https.address=:443"
      - "--certificatesresolvers.letsencrypt"
      - "--certificatesresolvers.letsencrypt.acme.storage=acme.json"
      - "--certificatesresolvers.letsencrypt.acme.email=webmaster@example.com"
      - "--certificatesresolvers.letsencrypt.acme.httpchallenge"
      - "--certificatesresolvers.letsencrypt.acme.httpchallenge.entrypoint=http"
      - "--providers.docker"
      - "--providers.docker.watch=true"
      - "--providers.docker.exposedbydefault=false"
    ports:
      - target: 80
        published: 80
        protocol: tcp
      - target: 443
        published: 443
        protocol: tcp
    volumes:
      - "/var/run/docker.sock:/var/run/docker.sock"
    restart: always

  db:
    image: mariadb:10
    container_name: nextcloud_db
    volumes:
      - "db:/var/lib/mysql"
    environment:
      - "MARIADB_RANDOM_ROOT_PASSWORD=yes"
      - "MYSQL_DATABASE"
      - "MYSQL_USER"
      - "MYSQL_PASSWORD"
    restart: always

  redis:
    image: redis:6-alpine
    container_name: nextcloud_redis
    environment:
      - "TZ"
    restart: always

  msmtpd:
    image: crazymax/msmtpd:latest
    container_name: nextcloud_msmtpd
    env_file:
      - "./msmtpd.env"
    environment:
      - "TZ"
    restart: always

  nextcloud:
    build:
      context: ./nextcloud
      dockerfile: Dockerfile
    container_name: nextcloud
    depends_on:
      - db
      - redis
      - msmtpd
    volumes:
      - "nextcloud:/data"
    labels:
      - "traefik.enable=true"
      - "traefik.http.routers.nextcloud.entrypoints=https"
      - "traefik.http.routers.nextcloud.rule=Host(`nextcloud.example.com`)"
      - "traefik.http.routers.nextcloud.middlewares=nextcloud-dav,nextcloud-wellknown"
      - "traefik.http.routers.nextcloud.tls=true"
      - "traefik.http.routers.nextcloud.tls.certresolver=letsencrypt"
      - "traefik.http.routers.nextcloud.tls.domains[0].main=nextcloud.example.com"
      - "traefik.http.services.nextcloud.loadbalancer.server.port=8000"
      - "traefik.http.middlewares.nextcloud-dav.replacepathregex.regex=^/.well-known/(card|cal)dav"
      - "traefik.http.middlewares.nextcloud-dav.replacepathregex.replacement=/remote.php/dav/"
      - "traefik.http.middlewares.nextcloud-wellknown.replacepathregex.regex=^(/.well-known.*)"
      - "traefik.http.middlewares.nextcloud-wellknown.replacepathregex.replacement=/index.php$$1"
    env_file:
      - "./nextcloud.env"
    environment:
      - "TZ"
      - "PUID"
      - "PGID"
      - "DB_TYPE=mysql"
      - "DB_HOST=db"
      - "DB_NAME=${MYSQL_DATABASE}"
      - "DB_USER=${MYSQL_USER}"
      - "DB_PASSWORD=${MYSQL_PASSWORD}"
      - "NEXTCLOUD_TRUSTED_DOMAINS=${NEXTCLOUD_TRUSTED_DOMAINS}"
    restart: always

  cron:
    build:
      context: ./nextcloud
      dockerfile: Dockerfile
    container_name: nextcloud_cron
    depends_on:
      - nextcloud
    volumes:
      - "nextcloud:/data"
    env_file:
      - "./nextcloud.env"
    environment:
      - "TZ"
      - "PUID"
      - "PGID"
      - "DB_TYPE=mysql"
      - "DB_HOST=db"
      - "DB_NAME=${MYSQL_DATABASE}"
      - "DB_USER=${MYSQL_USER}"
      - "DB_PASSWORD=${MYSQL_PASSWORD}"
      - "SIDECAR_CRON=1"
      - "CRON_PERIOD=*/5 * * * *"
    restart: always

  previewgen:
    build:
      context: ./nextcloud
      dockerfile: Dockerfile
    container_name: nextcloud_previewgen
    depends_on:
      - nextcloud
    volumes:
      - "nextcloud:/data"
    env_file:
      - "./nextcloud.env"
    environment:
      - "TZ"
      - "PUID"
      - "PGID"
      - "DB_TYPE=mysql"
      - "DB_HOST=db"
      - "DB_NAME=${MYSQL_DATABASE}"
      - "DB_USER=${MYSQL_USER}"
      - "DB_PASSWORD=${MYSQL_PASSWORD}"
      - "SIDECAR_PREVIEWGEN=1"
      - "PREVIEWGEN_PERIOD=0 * * * *"
    restart: always

  news_updater:
    build:
      context: ./nextcloud
      dockerfile: Dockerfile
    container_name: nextcloud_news_updater
    depends_on:
      - nextcloud
    volumes:
      - "nextcloud:/data"
    env_file:
      - "./nextcloud.env"
    environment:
      - "TZ"
      - "PUID"
      - "PGID"
      - "DB_TYPE=mysql"
      - "DB_HOST=db"
      - "DB_NAME=${MYSQL_DATABASE}"
      - "DB_USER=${MYSQL_USER}"
      - "DB_PASSWORD=${MYSQL_PASSWORD}"
      - "SIDECAR_NEWSUPDATER=1"
      - "NC_NEWSUPDATER_THREADS=10"
      - "NC_NEWSUPDATER_TIMEOUT=300"
      - "NC_NEWSUPDATER_INTERVAL=900"
      - "NC_NEWSUPDATER_LOGLEVEL=error"
    restart: always

  collabora:
    image: collabora/code
    container_name: nextcloud_collabora
    cap_add:
      - MKNOD
    labels:
      - "traefik.enable=true"
      - "traefik.http.routers.collabora.entrypoints=https"
      - "traefik.http.routers.collabora.rule=Host(`collabora.example.com`)"
      - "traefik.http.routers.collabora.tls=true"
      - "traefik.http.routers.collabora.tls.certresolver=letsencrypt"
      - "traefik.http.routers.collabora.tls.domains[0].main=collabora.example.com"
      - "traefik.http.services.collabora.loadbalancer.server.port=9980"
    environment:
      - "DONT_GEN_SSL_CERT=true"
      - "domain=nextcloud.example.com"
      - "extra_params=--disable-ssl"
      - "aliasgroup1=https://nextcloud.example.com"
    restart: always
  
volumes:
  db:
  nextcloud:

Hello @0x1ceKing, welcome to the Nextcloud community! :handshake:

what is your expectations using this hostname? you don’t own this domain (basically nobody can) so you can’t host anything there.

Hi, I’m a Cybersecurity Researcher and I’m trying to set up Nextcloud with Collabora and Mail locally for debugging purposes. I’m not very experienced with Docker, so I’d really appreciate any advice or guidance you can provide. Thanks u