Something that few people remember is that if you have access to a filesystem through SSH, then you can have a remote Git repository with no configuration!

In the remote machine, you only need to create a bare repository:

git init --bare

And in your "client" machines you use it like any other remotes:

git remote add my_remote my_user@my_host:path_to_repo

It can be useful if for some reason you don't want to use GitHub/GitLab/Bitbucket/etc or as a glorified scp