3650 Thunderbolt video?

Hi All,

I have a Precision 3650 that came from the factory with the Thunderbolt 4 PCIe card (7R4VG). The card works, I can attach TB4 drives and other accessories. I have not been able to use these ports to output video by DP over USB-C to an Asus ProArt278CV. I don't have a Thunderbolt Display to test this with. Do I need to use the Dell specific DP to DP cable (C19Y0) from the GPU to the TB4 card? Can these ports only output video to a true TB display, and not DP over USB-C?

Thanks!