Hello Andrea,
how about an overwrite in /etc/univention/templates/files/etc/apache2/sites-available/000-default.d/10univention-appcenter like?
if app and app.auto_mod_proxy and app.has_local_web_interface() and app_id == 'owncloud':
web_interface = 'cloud'
I’ve used a similar approach here to create a subdomain for nextcloud.
The above suggested code is really a very simple overwrite and of course it is always advised to not change the original template files. More, it only won’t break your apache setting if owncloud is the only app you are going to use.
But you could create your own vhost-template for this and register it. (In the linked thread - I think there is a ucr-command missing. You would have to run ucr update see in the docs )
Edit: the more I look at the code, the uglier it gets… but I still hope it helps to develop something nicer…
Best,
Bernd