By the way, for posterity:

I'm told that I could simply use the Time Machine backup system to roll back my system to 10.13.3. Since I religiously keep two redundant backups, this should theoretically be easy.

I hadn't realized that Time Machine could roll back the OS, I thought it was just for my documents. I've never actually needed to use its restoration features before.

I don't need to do it now, since I'm improving the video connections to remove my dependence on their support for DisplayLink, but it's worth noting that it would have been an option for me.