Thanks, Denpepe.
It turned out my Windows installation was corrupt. I did a clean install, the ASUS driver installer ran, and now Thunderbolt is working perfectly.
I found it here:
[URL]https://drivers.eu/Mainboards/ASUS/X299-DELUXE%20II?page_2[\url]
But the installer tells me it ended prematurely because of an error.
Thanks, but I don't see it at that link.
For Drivers & Tools you get (for Win 10) BIOS, Audio, LAN, Utilities, Wireless, Chipset, SATA, Bluetooth, Qualified Vendor List, and Utilities for OLED displays, but no Thunderbolt.
I've recently acquired a Thunderbolt equipped audio interface, and I'm trying to use it with my X299 Deluxe II.
I've enabled "Thunderbolt USB Support" in the BIOS. Following that, Win 10 shows a "Base System Device" with an error triangle. My audio interface also appears with an error triangle...