export DISPLAY=:0Having done that, I launched Firefox by typing:
firefox &on the command line. The ampersand is used in order to send the process to the background and keep the console usable.
Searching for KDE startup problems, I found the this post, explaining how to restart your KDE plasma desktop. I tried running "kstart plasma-desktop" and it gave me the following error:
"Application plasma-desktop could not be found using service org.kde.plasma-Searching for this message landed me on the KDE forum, where this post examined a similar problem.
desktop and path /MainApplication."
After reading it for a while, I concluded that I am most likely missing the plasma-desktop for some reason, so I decided to reinstall it using:
sudo apt-get install plasma-desktopWhile the reinstallation was executing I noticed that the MySQL server and client packages got installed again. It turned out that plasma needs MySQL to function and I have somehow confirmed the removal of plasma while removing MySQL.
After the reinstallation I rebooted from the command line and KDE Plasma started normally.
The takeaway from the story: Never do important reconfiguration without giving it a second thought and don't rely too much on the modern good looking Kubuntu tooling to save you from doing something stupid.