2017 iMac kernel panics after Catalina upgrade

I just want to document my issue here in case some people have the same problem.

I had a fully functioning computer running Mojave 10.14.6. I'm a video editor and have an older external thunderbolt 1 drive for my media (OWC Mercury Elite Pro Duo) hooked up to the mac via apple's usbc to thunderbolt adapter. Also lots of other usb peripherals and a second monitor with a usbc-dvi setup. So iMac was working fine on Mojave and I finally bit the bullet and upgraded to Catalina 10.15.5. The next morning (I updated it in the evening) the machine started having constant kernel panics (iMac locks up...black screen...reboot saying the system encountered a problem). This happened again and again.

Long story short it was the OWC thunderbolt 1 drive. Catalina did something that borked this drive or did something to the thunderbolt controller that the drive doesn't like. MAYBE the drive was just about to die anyway and it's a coincidence. I haven't tested another thunderbolt drive yet. For now am continuing my work just using a USB drive.

In my troubleshooting I was able to rule out software, the internal SSDs, the ram, and all the peripherals. When i'd exhausted all that it turns out taking that drive out of play solved the problem. The crashes also occured on a new install of Mojave (10.14.6) on this machine on a different boot volume. So it's something the Catalina install did that seems irreversible.

My specs:

iMac 18,3 (Retina 5K, 27-inch, 2017)

4.2 GHz Intel Core i7

64 GB 2400 MHz DDR4

Radeon Pro 580 8 GB