I am not aware of any native 8 bit or lower training, or for that matter, inference, as compared with something like tflite, which only supports it in specific instances.  Partially I assume this has to do with the fact that there is no canonical method for quantization.  There are a number of implementation examples though, see, e.g., https://github.com/eladhoffer/quantized.pytorch 20, or Glow.