This documentation is not working as is. It's only for reference. I am using my own mariadb on bare metal because mariadb in docker is very slow. Also i am using an external docker network for IPV6 subnetting.

In your Docker- Compose Directory, create the folder wordpress and a new file docker-compose.yml as always and add:

# Copyright Broadcom, Inc. All Rights Reserved.
# SPDX-License-Identifier: APACHE-2.0
services:
  wp:
    image: docker.io/bitnami/wordpress:latest
    stop_grace_period: 3m
#    ports:
#      - '80:8080'
#      - '443:8443'
    volumes:
      - wp:/bitnami/wordpress
#      - '/run/mysql/mysql.sock:/run/mysql/mysql.sock'
    environment:
      # ALLOW_EMPTY_PASSWORD is recommended only for development.
#      - ALLOW_EMPTY_PASSWORD=yes
      - WORDPRESS_DATABASE_HOST=mariadbserver
      - WORDPRESS_DATABASE_PORT_NUMBER=3306
      - WORDPRESS_DATABASE_USER=wp_user
      - WORDPRESS_DATABASE_NAME=wp_data
      - WORDPRESS_DATABASE_PASSWORD=SecureDBPassword
      - WORDPRESS_ENABLE_HTTPS=yes
      - WORDPRESS_SCHEME=https
      - WORDPRESS_EMAIL=Webmaster@domain.tld
      - WORDPRESS_ENABLE_REVERSE_PROXY=yes
      - WORDPRESS_ENABLE_MULTISITE=yes
      - WORDPRESS_MULTISITE_HOST=domain.tld
    networks:
      - wp_default

volumes:
  wp:
    driver: local

# Still needs to be defined while without it won't enable ipv6
networks:
  wp_default:
    external: true
    enable_ipv6: true

Attention:

• The User and Database with that Password has to be created before on your mariadb- instance.
• The above ENVs will create a setup-file of Wordpress in your Volume ( wp-config.php ) - check, that all your Setting are applied at first start.
  • After the first setup, the ENVs are never checked again and changes will have no effect at all !
  • You may edit the file in your Volume to apply new Values
• You can reach the Admins-User-Panel at https://domain.tld/wp-admin/profile.php . The Admin User and Password will be: user:bitnami
  • Please go to the Password- Section there and change your Password first before using that installation

Here you can find about the basic configuration of Bitnamis package: https://hub.docker.com/r/bitnami/wordpress

Now, edit your Caddyfile:

https://wp.domain.tld:443 {
        header Strict-Transport-Security max-age=31536000;
        reverse_proxy wp-1:8080
}