Where did my Emacs color-theme go in Ubuntu 20.04.LTS?!

Having recently upgraded a small VPS from Ubuntu 18.04.LTS to Ubuntu 20.04.LTS, I ran into a little snag with Emacs and its color-theme (from the emacs-goodies-el package).

After some digging, it seems this is now done somewhat differently in Ubuntu 20.04.LTS.

This is what my .emacs file used to contain:

(require 'color-theme) 
(color-theme-initialize) 
(color-theme-charcoal-black)

This is what I changed it to:

(add-to-list 'custom-theme-load-path 
(file-name-as-directory "/usr/share/emacs/site-lisp/elpa/color-theme-modern-0.0.2"))
(load-theme 'charcoal-black t t) 
(enable-theme 'charcoal-black)

In addition, I also had to install the elpa-color-theme-modern package (from the Ubuntu 20.04.LTS distribution).