If our repository doesn't stick to the conventional origin remote or has many remote repositories, we are not able to stale clean branches for theses ones.

We should be able to use both:

git clean-stale-local [-n|--dry-run] (using origin as default) or git clean-stale-local [-n|--dry-run] <remote name>.

We may also consider adding a global option, targeting all remotes: git clean-stale-local [-n|--dry-run] [-a|--all]