Comment 2 for bug 1784098

The reason the ubuntu-minimal package is not found is because you have disabled the release pocket for main and restricted. Your /etc/apt/source.list file contains the following:

  5 # deb http://it-mirrors.evowise.com/ubuntu/ xenial main restricted
  6 # deb-src http://it-mirrors.evowise.com/ubuntu/ xenial main restricted

If you were to uncomment those lines ubuntu-minimal will be found but your upgrade may fail for other reasons.