I am out for long time!
Well I think what is problem here. Ubuntu 18 does not come with some repositories on sources.list
I Resolve my problem for intalling fog on ubuntu 18 on that way! Running that: (If you run in root user, remove sudo, of course )
sudo echo "deb http://cz.archive.ubuntu.com/ubuntu bionic main universe" >> /etc/apt/sources.list sudo apt-get update
Now your FOG Installation it’s able to download all packages and install
Best Regards! I hope this helps!