Файл: /etc/apt/sources.list.d/official-package-repositories.list
deb http://packages.linuxmint.com sylvia main upstream import backport
deb http://archive.ubuntu.com/ubuntu xenial main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu xenial-updates main restricted universe multiverse
deb http://archive.ubuntu.com/ubuntu xenial-backports main restricted universe multiverse
deb http://security.ubuntu.com/ubuntu/ xenial-security main restricted universe multiverse
deb http://archive.canonical.com/ubuntu/ xenial partne
После:
apt update
apt upgrade
apt full-upgrade
Перезагружаем устройство:
sudo reboot