You've said several times that logging in via SSH always works. In that case, what do you mean by logging in "remotely"? To most people "remote" equals to SSH. Did you mean GUI? In that case - try to use on-screen keyboard app (built-into most OS) and type with your mouse.
Yes, I meant GUI, I said that at some points but I know this has become a long thread.
I dont like advising to "reinstall Linux to fix an issue" but you could be trying to track down a needle in a haystack here without a magnet (necessary skills). Hence, a fresh install may be in order.
Can you please go to work for [insert every tech company on earth] because the first thing in their "tech support" script is to reinstall or factory restore which should be the last thing! lol
Anyway, for the last 24 hours I have not had a single problem logging in locally, via ssh or gui. The problem appears to have resolved itself. I wonder if Linux has any "self healing" capabilities where it can fix minor problems it identifies? When I first ran journalctl -f I was seeing lines that were red and yellow which I assume were highlighted because they represented an issue. But I don't see them anymore, so if there was an issue causing my login problems maybe it has resolved itself.
Assuming the problem is gone, if I ever figure out what caused it I will come back to this thread and explain it for the benefit of anyone else who has this issue in the future and finds this thread.
Thanks for your help with this! At the very least it has forced me to learn a few things about Linux. Believe it or not I have a masters degree in Computer Science before Linux existed. I had to take a class in Unix and had to master the basics to use the computers in the lab. But that was a couple decades ago and I haven't used it since so all that knowledge exited the building a long time ago!