Well, I guess I sort of spoke too soon. Apple just released a Supplemental Update to macOS Catalina. This update is prior to Catalina 10.15.1, the “normal” first update. It fixes some of the Installation issues people have been experiencing (yours truly included). This article goes into more detail on what this Supplemental Update actually fixes. I updated my iMac with it, no problems. It was kind of slow to install, don’t know how big it is.