Hello @hskwon,
For your NVIDIA Tesla T4, I believe your BusID is “PCI:00:30:00” which is basically converting the hexadecimal “0:1E:0” to decimal. As a quick test, if you just run sudo nvidia-xconfig WITHOUT any options, the resulting xorg.conf file will show the correct BusID.
Provided that you’ve installed the NVIDIA drivers and necessary packages, you also don’t have to run sudo nvidia-xconfig -a --use-display-device=None --virtual=1280x1024 and instead, just run sudo nvidia-xconfig. The X server might not run if there is no display device specified in the xorg.conf.
Lastly, the T4 shows up as a 3D Controller because it is really optimized for 3D rendering and computational tasks rather than driving a display.
Hope this helps,
Tino