In case anyone is still having issues, I just got off support with Asus and their recommendation worked:
Update the intel chipset.
The files I got were:
V1828.12.0.1152_consumer_20181130_WHQL
Intel_Chipset_Installation_Utility_WIN10-64_V10.1.17695.8086
Granted, I tried everything under the sun before this, so it might not be as simple as updating the chipset. My problem was that the card would cause Windows to hang during start up. I fixed the master boot record, reinstalled windows about 8 times, tried several pcie slots, tried different versions of the driver, tried locking the pci thing through msconfig, virtually everything. All of this despite that the ac68 is on my motherboard's QVL!
In the end, here's what worked. I have a fresh installation of Windows 10. I downloaded the asus drivers from the website. I downloaded the two zip files above. I ran AsusSetup from the intel chipset zip and SetupME from the WHQL zip. My card works now.
Specs:
i7-8700k cpu
ASUS Z390-a PRIME motherboard