Nextcloud Cron [docker]

docker-compose.yml

version: '3.7'

services:
  app:
    image: nextcloud:apache

  cron:
    image: rcdailey/nextcloud-cronjob
    restart: always
    network_mode: none
    depends_on:
    - app
    volumes:
    - /var/run/docker.sock:/var/run/docker.sock:ro
    - /etc/localtime:/etc/localtime:ro
    environment:
    - NEXTCLOUD_CONTAINER_NAME=Nextcloud
    - NEXTCLOUD_CRON_MINUTE_INTERVAL=5

As TasyDevilsky pointed out, you can also use crontab:

On your system:

crontab -e

Add this line to the bottom */5 * * * * docker exec -u www-data Nextcloud php /var/www/html/cron.php

PS: Nextcloud is name of your container, if you used marketplace it should be Nextcloud :)