Maybe a basic question: If I download and install https://github.com/RTimothyEdwards/open_pdks, does this already contain xschem, magic, ngspice, etc., or do I need to install something extra? Can I ignore the specific "prerequisites" installation instructions in http://opencircuitdesign.com/open_pdks/ and http://opencircuitdesign.com/magic/ ? If the open_pdks container has copies of xschem etc., how do I access the containerized versions and not the versions I installed, maybe by accident, onto my native OS?

open_pdks is just a way to make the information from skywater more accessible to the tools that need it

I found that the open_pdks install did not work without Magic installed. That's because it needs Magic to make Magic files. Beyond that, while there were messages about downloading and installing the various tools in the flow, you could likely expect to see failures due to dependencies not being met. I would recommend going down the list of tools on the Open PDKs website, follow the links, and install them yourself one-at-a-time. That's what I did to get things working. It took a while, BTW.