My monorepo where I keep packages I repeatedly copy/paste into new projects, but that I don't want to publish to Pypi.
Libary code is in the libs/ directory. All packages should be isolated from each other, meaning you can copy the src/<package_name> directory from any library package into your project to get up and running. Check each library's pyproject.toml's [dendencies] section to see if you need to install any extra packages.