Отказ установить сбой Zentyal - недостающие зависимости

Я должен установить Сервер Zentyal на своем Ubunut для Школы, но во время этого процесса я встретился с некоторыми ошибками:

root@nasr-kmu2:~# sudo apt install zentyal
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:

The following packages have unmet dependencies:
 zentyal : Depends: zentyal-core but it is not going to be installed
           Depends: zentyal-software but it is not going to be installed
E: Unable to correct problems, you have held broken packages.

Из-за некоторых рекомендаций в Интернете я попробовал следующее, но ничто не помогло.

root@nasr-kmu2:~# sudo apt-get install -f
Reading package lists... Done
Building dependency tree       
Reading state information... Done
0 upgraded, 0 newly installed, 0 to remove and 0 not upgraded.
root@nasr-kmu2:~# 

Какие-либо идеи?