That's because CUDA is only for Nvidia GPUs and Apple doesn't support Nvidia GPUs, it has its own now.

Didn’t apple stop supporting Nvidia cards like 5 years ago? How could it be confusing that Cuda wouldn’t run?

Ah, I didn't realize. It's not very obvious what GPU you have in your Macbook, I couldn't actually find out where to find that in my System settings. On Windows it's inside the "Display" settings but on MacOS... where is it? :)

lol presumably the OP didn't know that... hence the confusion.

    (base)   stable-diffusion git:(main) conda env create -f environment.yaml
    Collecting package metadata (repodata.json): done
    Solving environment: failed
    
    ResolvePackageNotFound:
      - cudatoolkit=11.3

oh i was following the github fork readme, there is a special macos blog post

link?