Recently, I could not log in on a regular user desktop installation through the graphical login screen. However, I was able to successfully log in by switching (CTRL+ALT+F1) to terminal mode. Eventually, through the terminal mode I resolved the problem.
In researching my issue, on the Ubuntu forum; I noticed that there were numerous causes concerning the inability to use the graphical login screen. Which made finding the correct fix difficult. The simplest approach would seem to be a total "tear-down" of the graphical interface with a rebuild to resolve the login issue instead of spending a significant amount of time attempting to isolate a specific cause. Essentially applying a "nuclear option". After extensive research and numerous dead-ends; I found out my problem was caused by "brltty", but that is not my question.
My question: A listing of the packages that need to be removed so that Ubuntu simply boots into terminal mode (no graphical interface). Then a sequential listing of what packages need to be reinstalled to restore the graphical interface (which I assume are the same packages that were removed). Basically, a short tutorial on removing the graphical interface and rebuilding it.