Ubuntu installation process assumes that main and universe are enabled

[Francesco Zardi]

Describe the bug
The README recommends the user runs:

sudo apt install imagemagick

but this fails on a clean Ubuntu installation because the main and universe repositories are not enabled:

E: Package 'imagemagick' has no installation candidates

To Reproduce
Steps to reproduce the behavior:

1. Download Ubuntu 22.04.3 LTS live image ISO
2. Create a clean VM and run the live image
3. Follow the t-rec installation steps from the README

Expected behavior
Installation should be completed without error.

Version Numbers of your System:
just run: inxi -SGxx and paste it below:

System:
  Host: ubuntu Kernel: 6.2.0-26-generic x86_64 bits: 64 compiler: N/A
    Desktop: GNOME 42.9 tk: GTK 3.24.33 wm: gnome-shell dm: GDM3
    Distro: Ubuntu 22.04.3 LTS (Jammy Jellyfish)
Graphics:
  Device-1: VMware SVGA II Adapter driver: vmwgfx v: 2.20.0.0 ports:
    active: Virtual-1 empty: Virtual-2, Virtual-3, Virtual-4, Virtual-5,
    Virtual-6, Virtual-7, Virtual-8
    bus-ID: 00:0f.0 chip-ID: 15ad:0405
  Display: x11 server: X.Org v: 1.21.1.4 compositor: gnome-shell driver: X:
    loaded: vmware unloaded: fbdev,modesetting,vesa gpu: vmwgfx display-ID: :0
    screens: 1
  Screen-1: 0 s-res: 1918x1085 s-dpi: 96
  Monitor-1: Virtual1 mapped: Virtual-1 res: 1918x1085 size: N/A
  OpenGL: renderer: llvmpipe (LLVM 15.0.7 256 bits)
    v: 4.5 Mesa 23.0.4-0ubuntu1~22.04.1 direct render: Yes

Output of lsb_release -a:

Distributor ID:	Ubuntu
Description:	Ubuntu 22.04.3 LTS
Release:	22.04
Codename:	jammy

Additional context
Add any other context about the problem here.

Please include the output of xwininfo -root -tree -int

xwininfo: Window id: 1336 (the root window) (has no name)

  Root window id: 1336 (the root window) (has no name)
  Parent window id: 0 (none)
     35 children:
     23068673 "update-notifier": ("update-notifier" "Update-notifier")  10x10+10+10  +10+10
     4194314 "gnome-shell": ("gnome-shell" "Gnome-shell")  1x1+-200+-200  +-200+-200
        1 child:
        4194315 (has no name): ()  1x1+-1+-1  +-201+-201
     39845898 "ubuntu@ubuntu: ~": ("gnome-terminal-server" "Gnome-terminal")  1848x1058+70+27  +70+27
        1 child:
        39845899 (has no name): ()  1x1+-1+-1  +69+26
     39845894 (has no name): ()  1x1+-1+-1  +-1+-1
     48234497 "Calendar": ("gnome-calendar" "Gnome-calendar")  10x10+10+10  +10+10
     39845890 "Terminal": ()  10x10+-100+-100  +-100+-100
     44040193 "seahorse": ("seahorse" "Seahorse")  10x10+10+10  +10+10
     39845889 "Terminal": ("gnome-terminal-server" "Gnome-terminal-server")  10x10+10+10  +10+10
     33554440 (has no name): ()  1x1+-1+-1  +-1+-1
     33554435 "@!0,0;BDHF": ("gjs" "Gjs")  1918x1085+0+0  +0+0
        1 child:
        33554436 (has no name): ()  1x1+-1+-1  +-1+-1
     33554433 "gjs": ("gjs" "Gjs")  10x10+10+10  +10+10
     31457281 "snapd-desktop-integration": ("snapd-desktop-integration" "Snapd-desktop-integration")  10x10+10+10  +10+10
     4194330 (has no name): ()  1x1+-1+-1  +-1+-1
     29360130 (has no name): ("" "")  1x1+-100+-100  +-100+-100
        1 child:
        29360131 (has no name): ()  1x1+-1+-1  +-101+-101
     27262979 "ibus-xim": ()  1x1+0+0  +0+0
        1 child:
        27262980 (has no name): ()  1x1+-1+-1  +-1+-1
     27262977 "ibus-x11": ("ibus-x11" "Ibus-x11")  10x10+10+10  +10+10
     25165825 "evolution-alarm-notify": ("evolution-alarm-notify" "Evolution-alarm-notify")  10x10+10+10  +10+10
     16777218 (has no name): ()  10x10+0+0  +0+0
     20971521 "ibus-extension-gtk3": ("ibus-extension-gtk3" "Ibus-extension-gtk3")  10x10+10+10  +10+10
     18874369 "gsd-color": ("gsd-color" "Gsd-color")  10x10+10+10  +10+10
     14680065 "gsd-wacom": ("gsd-wacom" "Gsd-wacom")  10x10+10+10  +10+10
     16777217 "gsd-xsettings": ("gsd-xsettings" "Gsd-xsettings")  10x10+10+10  +10+10
     12582913 "gsd-power": ("gsd-power" "Gsd-power")  10x10+10+10  +10+10
     10485761 "gsd-media-keys": ("gsd-media-keys" "Gsd-media-keys")  10x10+10+10  +10+10
     8388609 "gsd-keyboard": ("gsd-keyboard" "Gsd-keyboard")  10x10+10+10  +10+10
     4194323 "gnome-shell": ()  10x10+-100+-100  +-100+-100
     4194321 (has no name): ()  1x1+-100+-100  +-100+-100
     4194319 (has no name): ()  1x1+-100+-100  +-100+-100
     4194318 (has no name): ()  1x1+-1+-1  +-1+-1
     4194312 (has no name): ()  1x1+-100+-100  +-100+-100
     4194311 (has no name): ()  1x1+-100+-100  +-100+-100
     4194310 "GNOME Shell": ()  1x1+-100+-100  +-100+-100
     4194305 "gnome-shell": ("gnome-shell" "Gnome-shell")  10x10+10+10  +10+10
     2097160 (has no name): ()  1x1+-100+-100  +-100+-100
     4194320 "mutter guard window": ()  1918x1085+0+0  +0+0

[Francesco Zardi]

I believe the README could be extended to enable the main and universe repositories:

sudo add-apt-repository main
sudo add-apt-repository universe
sudo apt-get update
sudo apt-get install imagemagick