Our friends from InformAzioni.wiki would love to adopt our nextCloud instance, migrating from proprietary services. But actually the Calendar plugin is somehow borked.
First of all we need to upgrade our ownCloud instance from ownCloud to nextCloud. The one served by the Reyboz server.
I've already tried a month ago but the upgrade from 10.3.0 (stable) to the suggested nextCloud 12.0.12 failed, so we need to retry with smaller steps.