@Aravisian seems the broken packages are holding back the sought after corrections.
If I wasn't using the Software Store, Software and Updates nor the Software Updater, I don't know if I could tell anything was awry. (I have the popOS store now.) But I suspect the chasm will only get wider over time.
You said when this happened to you earlier, it took a lot of time and effort. I don't think I have the understanding yet to do all that may be required. And I don't want to impose on you for all the help it sounds like this could ultimately require.
I have two more questions I will humbly ask, if you don't mind, and then if they have no merit, I think I will go the reinstall route. One difference between your experience with doing upgrades over temporary repositories and mine is that you forgot to remove the repositories. In my case, I didn't know I needed to. So this is at least one more thing I am learning about Linux in this scenario.
My questions is related to the files I should remove from /etc/apt/sources.list/.d. First, the files I removed were not explicitly labeled as popOS repositories to my newbie eyes. The files were named approximately "popOS-stable-focal.list" and "popOS-stable-focal.list.save". Do these look like the repository files you were asking me to remove?
Everything else in this folder has ZorinOS in its name except for the following two files: "xubuntu-dev-ubuntu-staging-focal.list" and "xubuntu-dev-ubuntu-staging-focal.list.save". Should I try removing these two files, too?