PGAdmin is a WEB- GUI for Postgres Databases e.g. for Nextcloud.

To Setup that Service, create a Folder named pgadmin in your docker_compose directory you created before when setting up docker

Create the docker-compose.yml like this:

services:
  pgadmin:
    image: dpage/pgadmin4
    environment:
      PGADMIN_DEFAULT_EMAIL: admin@domain.tld
      PGADMIN_DEFAULT_PASSWORD: NEWPASSWORD
    volumes:
      - pgadmin_data:/var/lib/pgadmin/
    networks:
      - nextcloud-aio

volumes:
  pgadmin_data:
    driver: local

networks:
  nextcloud-aio:
    external: true

Append to the Caddyfile of docker-caddy