Thanks for the Answer.

Yes i have configured the Provider.
My Configuration:

But if I clone a repository, then this has the following remote:

git@nyx.hausformat.net:group/reponame.git

Is this feature only available with gitlab.com, or should it work also with a self-hosted GITLab?

I tried the Preview 10 and could not activate/find the merge-request of the Repo.

I have cloned the project with the appropriate hosting provider.