Thanks to this new and interesting news:
https://discussions.apple.com/thread/8339158

I no longer have a working docking station solution for dual external monitors. I updated my Mac OS without knowing that it would break my external HDMI monitors.

I have a special need which requires me to have the ability to swap out which laptop I'm using on my dual monitors on my home desk. I swap between my home laptop, my work laptop, and my mac, depending on the situation. When all three devices supported DisplyLink, it was easy, I could just plug them into the dock. Now... not so much.

I can also use a Mac USB-C Digital AV Multiport Adapter successfully, but that gets me only one external HDMI monitor, not two. In fact, I have been successfully doing a hybrid where monitor 1 is driven off the HDMI plug from that thing, and monitor 2 is driven off the DisplayLink dock, for quite a while. But now, the second DisplayLink display just goes black.

I could upgrade to a pair of "Thunderbolt 3" monitors at great expense, and then my mac would work, but then my PCs wouldn't work with those monitors when I needed to do stuff on them. (would they? I don't understand the relationship between USB3 and Thunderbolt 3.) Problem is that all the new displays are super high rez, and honestly, what I really want is a pair of old 1920x1080 displays like I've currently got because the new super high rez displays are way too fine for my aging eyesight.

Also, I have this thing where one of the HDMI plugs going to one of the monitors goes to a HDMI splitter that goes to the TV next to the recording booth, allowing me to see/control the DAW from the booth. That's super useful and I don't want to lose that either.

I could become the operator from The Matrix and have four monitors I suppose, two PC and two mac. Again: expense of the extra monitors and added mounting bracketry.

I wonder if I'd be happy with one super ultra wide screen instead of two regular screens? Those are pricey too, though, and I have no idea if my Windows laptops' HDMI ports would even support it.

Any other ideas of what would work for me?

This sucks because I had a working system that I was happy with, even though it was kinda frankenstein, it worked, and now a software updated fried it all.