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).