How to reproduce:
Check the APT sources:
official repo in /etc/apt/sources.list.d/official-package-repositories.list
What to expect:
You should see the following:
cdrom repository (commented or removed post-install)
Linux Mint repository
Ubuntu repositories (codename, codename-updates, codename-backports and codename-security)
The following components for Linux Mint: main upstream import backport
The following components for Ubuntu: main restricted universe multiverse
Romeo should not be enabled.
Source repos should not be enabled.