DRM_IOCTL_WAIT_VBLANK on RTX2060 with V470.63.01 Ubuntu 20.04.3 Driver does not work

Hi Folks! The NUC 11 PH7iKC Kit has the integrated NVIDIA GeForce RTX 2060. After setting up Ubuntu 20.04.3, and installing the latest NVIDIA 470.63.01 drivers, we found an application we have that monitors the VBLANK signal using drmIoctl(…, DRM_IOCTL_WAIT_VBLANK) ) also tried drmWaitVBlank(). It now returns “Operation not supported”. As a note, the 460 version of the driver did not work (no picture at all). The NVIDIA GTX1060 works fine, as do Intel 915 and Radeon devices. This seems to be new with the RTX 2060 (and NUC 11). Does anyone know of a way to accurately determine when a VBlank occurs on the RTX2060 under Ubuntu 20.04? (I also tried under Ubuntu 18.04 using the V470 driver and it does not work there either.)

secure boot should be disabled.