After updating to new Nvidia drivers 465.89, the game doesn’t see DX12 option. In GPU info it has DX12 listed as supported.
What GPU do you have? Also if your CPU has an iGPU double check if WoW isn’t looking at the iGPU instead.
Usually this is indeed related to the game trying to use the wrong GPU and can be fixed by swapping it over as mentioned above.
I’m on Ryzen system, no iGPU option. The change happened after driver update, I assume it will be fixed in next one, and currently is turned off by Blizz/Nvidia (as it sometimes happened), but can’t be sure. I guess I will wait.