For local projects I'm using a repo per module/package, creating tagged releases, and pushing them to a local package hosting server. I can then reference those artifacts as dependencies in the projects that need/use them. No need for complex CI pulls, just coordinated releases.

I also have a template repository I use to help with common setup for different project types so I don't need to repeat that every time I create a new project.

For Python it's easy to create an artifact server as the artifacts are just wheel files in a directory with the server listing the directories (packages), files (releases), and downloading the files.

I'm not sure about other artifact servers for other projects.