In general, it is recommended to use Homebrew to install MiGA if possible. The MiGA installation in macOS using conda is known to be fragile and extremely time-consuming (it could take upwards of 20 minutes just solving the environment).
Now, install all the required packages using conda:
# Install prerequisites
curl -Lso miga.yml \
conda env create -f miga.yml
# Tell MiGA to activate the proper conda environment
echo 'eval "$(conda shell.bash hook)" && conda activate miga' > ~/.miga_modules
# Activate the environment