Are you able to run the DCGAN example on the GPU or is it using your CPU?
I just cloned your repo and tried to run it.
It looks like my GPU was detected:
Number of colour channels: 4
Running on device: cuda

However, I get an error after these lines:
terminate called after throwing an instance of 'c10::Error'
  what():  Error opening images file at ./mnist/train-images-idx3-ubyte (read_images at /pytorch/torch/csrc/api/src/data/datasets/mnist.cpp:66)
frame #0: std::function<std::string ()>::operator()() const + 0x11 (0x7fa06a35bb91 in /home/pbialecki/libs/libtorch_nightly/libtorch/lib/libc10.so)