There is also somewhere a step to set up an alias for occ that can be used outside the container to directly execute occ cli commands inside the container.
Set default_phone_region like this: occ config:syste:set default_phone_region --value="DE"
Check if you have to alter this line in the collabora/loolwsd.xml file:
<host desc="Regex pattern of hostname to allow or deny." allow="true">nextcloud\\.sporada\\.eu</host>
Look at the documentation for server security and server tuning: https://docs.nextcloud.com/server/21/admin_manual/installation/index.html#