I respectfully disagree. In my opinion, guessing is appropriate when I am almost entirely ignorant of the inner workings of a system that has a problem. It’s like a Black Box experiment. If this were science, they’d call it forming a hypothesis, which would then be subjected to experiment to support or falsify it.
Your suggestions have been enormously helpful to me. I am genuinely grateful for that.
However, I feel that it is important for me to understand what’s going on. If I am lazy and just let you give me all the answers, then I may restore the system, but I will likely not understand what happened.
For example, you suggested that I get the information from inxi. I did that. I then tried to see whether I could find anything that offers a hint as to the problem. Similarly with the lightdm.conf file - and other configuration files I have hunted down. I felt I should at least make an effort to do some work on my own, instead of just sitting back and letting you and others do it for me.
I will post the results of the commands you suggested, when I am able to do so. I’m not ignoring your advice, I’m just trying to understand as I go along.