Once after installing Ubuntu Server 18.04, when trying to install Midnight Commander, a message was displayed that the package for installation was not found.
To solve the problem, you need to add the Universe repository:
sudo add-apt-repository universe sudo apt update
After this, the Midnight Commander should successfully install:
sudo apt install mc
If necessary, the Universe repository can be disabled as follows:
sudo add-apt-repository --remove universe
See also my article:
Installation and information about Midnight Commander on Linux
Watch the video on how I installed Midnight Commander (MC) on Ubuntu 18.04: