Dear @andre.a.bauer,
we were facing a similar issue recently and figured out, that the TensorRT binaries of for the Jetson do also work on the DriveAGX. The Jetson has a much faster release cycle and TRT 7 is available for it. It can be downloaded from here and the binaries copied to the DriveAGX manually. Just keep in mind that, while this worked for our purpose, this is not officially supported and functionality is not guaranteed.