i had a read through but I couldn't figure this out: What does it improve on compared to jsut regularly doing a git pull and git push to a different origin?

Also, can the destination be something other than GitLab?

Goal is to do a full mirror repo to repo incl. all branches in an automated way. It's indeed nothing else than a git pull, git push but automated (with API key). Yes the destination can be different but a provider needs to be developed for that (currently only GitLab & GitHub supported). Developed this to have a full local mirror of all my GitHub projects; but it can also work the opposite way; where you have a local GitLab you want to mirror to GitHub.