Thanks.
I have tried using Nvidia NGC container with Pytorch.
(PyTorch | NVIDIA NGC 35)
Using this, it seems CUDA works (torch.cuda.is_available() returns TRUE.)
I will use the container for now for Pytorch. (It is better if I could use it with local environment, but it seems current solution is  reinstalling CUDA driver, and I am afraid this may cause further confusions and eventually lead to factory reset… considering my configuration skills)