Hi Belyache, sorry for my question that will look stupid to you, but root cannot access cron.php via docker.
So I tried to run the same task as you with:
docker container exec --user www-data -it nextcloud.domain php cron.php
Even if it works in ssh, it does not via the task scheduler (root).
Do you have an advice on how to trigger the php cron.php job within docker?