You would need to rebuild PyTorch on JetPack 4.x for Python 3.8 - the normal instructions for building PyTorch on Jetson are included at the top of this thread. However, here are some other posts on it for Python 3.8:
- PyTorch for Jetson - #1053 by sealev (this one includes a link to the compiled pip wheel)
- Install PyTorch with Python 3.8 on Jetpack 4.4.1 - #3 by patrick.nagelm8t1h
- The instruction of installing Pytorch and TorchVision by Python3.8 on Ubuntu 20.04 on Jetson device