Setup SSH for and push to multiple Git-hosting service accounts (including self-hosted) from scratch
Thanks to Rodney Lorrimar for Pushing to Multiple Git Repos
This example uses two GitHub accounts, and a self-hosted GitLab account (localhost:8092 for ssh).
The Github (another-user account) private repo has been arbitrarily chosen as the main repo for the project.
The mirrors are a separate Github (wellknownuser account) public project, and a Gitlab (dubioususer account) private group and project.