Conda-forge recently (a year ago) added a new meta-package for libstdc++ called libstdcxx. We should add special handling for it the same as for libstdcxx-ng.
And then use it in PythonCall.
See https://discourse.julialang.org/t/version-cxxabi-1-3-15-not-found-when-loading-matplotlib-through-pythoncall/131671/17?u=cjdoris