No dice on my 1700x with 16GB installed. Still had to disable 4GB or it wouldn’t boot I deleted the UEFI partition off my USB drive and rewrite the bootsector from the installer.
I was able to boot by enabling the 4GB limit, disabling the radeon_hd accelerant (crashes during boot with Vega FE), and enabling failsafe video output (don’t think I had to do this before but it kept saying it couldn’t initialize the video output over and over… basically hung) it was either that or setting the video mode to 1366x768 32bit… not sure.