I have successfully compiled OpenCV 4.6.0 with CUDA and GStreamer for the AGX Orin.
A link not to be forgotten :
$ sudo chmod +x install_opencv4.6.0_Jetson.sh
$ ./install_opencv4.6.0_Jetson.sh
It works great. Many thanks @AastaLLL !
I just had to add Python 3.8 site package PATH to launch JetsonSky with IDLE (otherwise it could not load cv2).
Alain