Hi everybody,
I was struggling with a problem during the fog’s installation in Ubuntu Server 20.04 LTS. 
In the image, I show the error.
And I just was posting this message, because fortunately, I could resolve it and so, I would like to share with all the fog community, in case of someone else was in the same situation.
Therefore, in my case, i just had to execute the following commands:
apt-get update
apt-get dist-upgrade
apt-get autoclean
apt-get clean
apt-get autoremove
After these commands, I come back to execute fog (./installfog.sh) and the installation finished ok.
I’m hoping to contribute something with this post.
roro.