So I switched my setup to the B550-Creator board specifically because it has Thunderbolt 4 onboard. I've run the board mostly happily for a few months now (it seems slightly less table than the Prime X570-Pro board I replaced, but whatever). Today I finally changed my desk setup and connected the CalDigit TS3 Plus dock that I got to use the Thunderbolt with. Thunderbolt simply does nothing at the moment.
Windows detects the TS3 Plus in Device manager, but it appears like it just sees it as a general USB hub (and as such it does nothing). No Thunderbolt devices show up in Device Manager anywhere. Not broken or active, they just are not in Device Manager like the board doesn't have Thunderbolt. Thunderbolt Software also detects nothing. The light on the TS3 Plus is blue indicating it is powered & connected to the PC.
I've installed the latest Thunderbolt Software from Asus' website, update chipset drivers, tried BIOS version 2803, 3002, and 9902 (a beta ASUS provided someone else that was having TB issues). It feels like there is some BIOS toggle I'm completely missing. Armoury Crate also doesn't give me any option for Thunderbolt drivers, I had to go to the download page for the board to get them.
Anyone have any ideas what I'm missing? Is it maybe that I have a capture card in PCI-E 16x slot 3? Removing that is likely my next step. The manual indicates TB & that slot share lanes, but not that it will cause a conflict (except with DisplayPort, but I'm not using that).
Update: Removing the Elgato 4k60 mk2 capture card from my 3rd PCIe-16x slot did in fact seem to fix it. Started back up the pc and Thunderbolt just worked.
Gonna try putting the capture card back in shortly and hope that TB just needed a wakeup call... Doubt it will work, but worth a shot.
ANSWER: ASUS confirmed today that the 3rd PCI-e 16x slot "Shares Bandwidth with the Thunderbolt controller". I saw this in the manual but it was not clear that it actually means "You can use one or the other, but not both.". So I had to remove a card from my PC to make Thunderbolt work, leaving me stuck without a capture card at the moment. Unfortunate as I absolutely looked into this before purchasing the motherboard. I guess it is time to start considering ThreadRipper for my needs. As if I want to massively overpay just to get connectivity.