For JetPack 5.0, we provide the pre-built PyTorch wheel for Python 3.8 (as this is the default version of Python that comes with Ubuntu 20.04). For Python 3.9, you would need to build it from source, following the instructions from this post: https://forums.developer.nvidia.com/t/pytorch-for-jetson-version-1-11-now-available/72048 (that is, assuming you don’t want to just use Python 3.8 instead)