So, I had a bit of a shock today.  I haven't rebooted my Mac for a long time, and after having locked my updates on 1903 for a couple of years, and when I restarted my machine Microsoft appeared to force an update on me to Windows 1909.  At first I was super pissed because I knew it would break my eGPU (1909 has NEVER worked for me), but by that point I was in the blue "Windows is configuring your updates" shutdown screen, so I had to let it run, and sure enough, black screen on reboot.

So, I pulled the HDMI cable out of the eGPU enclosure and the thunderbolt cable connecting it to the Mac and booted into Windows with just the CPU with onboard graphics and thought "fuck it, maybe I'm done then.  Embedded graphics for me from now on..."

I thought I might as well update Windows completely to the very latest version and install pretty much everything if that was going to be my future.  I also installed 2 Apple Boot Camp updates at the same time.

Then on a whim I decided just to see (with zero percent faith) whether it might somehow magically boot with the eGPU attached again.  I pulled the HDMI out of the Mac and put it back into the back of the eGPU enclosure, connected the thunderbolt cable and... well fuck me!  It's working a treat.  Fully patched, fully up to date Windows 10 with eGPU working fine.

I've rebooted half a dozen times, opened the Radeon graphics app and changed a few settings, run a few games etc. just to make sure it's all working because I could hardly believe it.