Edit config php for trust domain. what is the command? what is the path?

First of all, thank you very much. It worked perfect. I am so grateful.
Secondly, and for learning purpose, where should the path for the file be? It seems to me very easy to edit the php file, the problem is the location. I have to say that it is a fresh new install of the appliance. I haven’t done any changes by myself nor did i upgraded by myself. I just downloaded the appliance from here and installed it

I tried several paths:
sudo nano /var/lib/univention-appcenter/apps/nextcloud/conf/config.php
sudo nano /var/www/nextcloud/config/config.php
sudo nano /var/www/html/nextcloud/config/config.php

None of the above commands opened the config.php file
I am a person that likes to learn new things especially because it is a fresh new install so i was wondering where can the file be located. Could the system upgraded itself automatically on a new install? if so can it be located in other places? in what paths? do you have ideas?