Where are my app logs?

I am trying to set up a fairly simple server and have a few issues. Obviously, the first thing to look for are the log files.
The only two apps I would need so far are letsencrypt and nextcloud. As such I have looked for their respecitve log files:

Administrator@nextcloud:/$ sudo find . -name letsencrypt.log
[sudo] Mot de passe de Administrator : 
Administrator@nextcloud:/$ sudo find . -name nextcloud.log

Is it nornal that I don’t have a letsencrypt.log file ? The app seems installed (at least it shows as such in the portal and I can get to the settings files).
More surprising (but I guess this is some container trick ?) I don’t have a
directrory ! Where is my log file ??

Nextcloud stores its log file inside the data directory (configuration setting datadirectory). For the Nextcloud app this is /var/lib/univention-appcenter/apps/nextcloud/data/nextcloud-data. However, Nextcloud runs inside a Docker container, which means that the setting refers to a directory with that name inside the Docker container.

In order to retain the data across Docker container upgrades, a directory on the host is bind-mounted to the directory inside the container. In this particular case the directory on the host is also called /var/lib/univention-appcenter/apps/nextcloud/data/nextcloud-data.

So yeah, the log file can be found as /var/lib/univention-appcenter/apps/nextcloud/data/nextcloud-data/nextcloud.log both inside the container and on the host.

You certainly do. Otherwise find wouldn’t have output the entry. I guess it’s a simple user error. Just try to open /var/lib/univention-appcenter/apps/nextcloud/data/nextcloud-data/nextcloud.log