Fresh Catalina install freezing at ~80%/2 minutes remaining

A few years ago I built a vanilla, Clover/High Sierra machine (hardware/stats at bottom of post) which I was dual-booting with Windows 10 and it was working perfectly. However, I had a EVGA GTX 1070 and was blocked from upgrading to Mojave or Catalina. I later added a EVGA GTX 2060 Super for Windows games and hid it from macOS using a DeviceProperties patch (per the instructions here). Everything still ran smoothly with Nvidia web drivers.

Last week I finally decided to upgrade to a new mobo/processor for a couple reasons (better connectivity options, new memory, faster processor, etc) and decided to throw in a Catalina-ready GPU while I was at it (Sapphire RX 580) so I could finally update my installation. (Again, hardware/stats below.)

I've been throwing everything I can at a new vanilla install for Clover/Catalina but am stumped. When I dropped in the SSD with my old High Sierra installation I removed the Nvidia web drivers and it worked pretty much flawlessly. For Catalina, I've been installing onto a spare SSD to iron out any kinks but I can't get any further than ~80%/2 minutes remaining on the Catalina installer. I started with a totally fresh config.plist and the latest build of Clover and just tried doing the KALSR slide value fix (memmap dump here) after getting a few missing slide/page allocation errors. The mobo is flashed to the latest available from Gigabyte (Dec '19). I've also removed the GTX 2060 Super card from the new mobo entirely to get any of those issues off the board. Any recommendations for where I can go next?

Old/High Sierra Hardware, Working * Mobo: Gigabyte Z97X-Gaming 7 * CPU: i5-4690k * GPU: EVGA GTX 1070 (EVGA GTX 2060 Super, ignored in DeviceProperties)

New/Catalina Hardware, Not Working * Mobo: Gigabyte z390 Aorus Pro * CPU: i7-9700k * GPU: Sapphire RX 580 (EVGA GTX 2060 Super, not installed, hope to re-install and ignore in macOS)