Comment 15 for bug 1840232

Notes / Observations:

(1)
You do not need to use sudo in your script because you are logged in as root in Cubic's chroot environment,

(2)
The default sources.list file already has bionic, bionic-security, and bionic-updates.

    $ cat /etc/apt/sources.list
    $ deb http://archive.ubuntu.com/ubuntu/ bionic main restricted
    $ deb http://security.ubuntu.com/ubuntu/ bionic-security main restricted
    $ deb http://archive.ubuntu.com/ubuntu/ bionic-updates main restricted

As a result, /etc/apt/sources.list.d/temp.list will contain duplicated repositories.
This isn't a big deal. However, another approach could be to use `sed` to add "universe" and "multiverse" to the existing lines...

    # Backup original sources.list
    $ cat /etc/apt/sources.list
    $ cp /etc/apt/sources.list ~/

    # Update sources.list
    $ sed -i "s|restricted|restricted universe multiverse|g" /etc/apt/sources.list
    $ cat /etc/apt/sources.list

    # (Install your applications and updates)

    # Restore original sources.list
    $ cp ~/sources.list /etc/apt/sources.list
    $ cat /etc/apt/sources.list

(3)
You can bypass the user input screen when installing mscorefonts...

    $ echo 'ttf-mscorefonts-installer msttcorefonts/present-mscorefonts-eula select true' | debconf-set-selections
    $ echo 'ttf-mscorefonts-installer msttcorefonts/present-mscorefonts-eula seen true' | debconf-set-selections
    $ echo 'ttf-mscorefonts-installer msttcorefonts/accepted-mscorefonts-eula select true' | debconf-set-selections
    $ echo 'ttf-mscorefonts-installer msttcorefonts/accepted-mscorefonts-eula seen true' | debconf-set-selections
    $ debconf-show ttf-mscorefonts-installer

    $ apt install -y ttf-mscorefonts-installer

(4)
Cubic calculated checksums for 331 files, for ubuntu-18.04.3-desktop-amd64.iso. You should have the same number when you run Cubic.