You say "Create a env.yaml file with the content above" however the content is below not above.
You say "conda env update -n nmy-env -f conda-env-gpu.yml;conda activate my-env;"
This seems to have several typos? i. nmy-env, ii. Your previous file was called env.yaml iii. Your previous example called the environment py-env not my-env, you mention conda-env-gpu.yml here but that wasn't mentioned previously?