Thanks folks!
I am going to try to implement this in Fedora 38.
There is one bit of the spec I don’t fully understand, but maybe I have missed this somewhere else in the PEP. I’m trying to follow the recommendation for the distros. tl;dr I want pip to install to /usr/local/lib(64)/python3.X/site-packages for the users, but RPM to install to /usr/lib(64)/python3.X/site-packages. We currently do this already, but we use the same syconfig installation scheme – I understand that we will need to change that to have two schemes and I accept that.
To follow the specification, we will put the EXTERNALLY-MANAGED marker file to /usr/lib(64)/python3.X/ because that is what sysconfig.get_path("stdlib", sysconfig.get_default_scheme()) returns.
However, for the new installation scheme that uses /usr/local/lib(64)/python3.X/site-packages, stdlib is still located at /usr/lib(64)/python3.X – there is no stdlib in /usr/local/lib(64)/python3.X. How do we make the marker not affect installations to /usr/local/lib(64)/python3.X/site-packages?