Cannot checkout submodules

Guys, I am a bit confused about submodules. I know regular git submodules and I think I can work with them without problems. But now I have got access to a (private) GitLab reprository which contains submodules. But I fail to check them out properly. For me they do not look like regular git submodules. :frowning:

Since the repo is private I cannot show a live link but it looks like this in the files view:

(sorry for obfuscating the names but since it is not my repo and it is private I think it would be fair to not show contents)

So it seems like all the entities suffixed by “@” are supposed to be submodules. The submodules refer to other projects inside the same GitLab repo. But after I checkout the project using “git clone” all the submodule directories do exist but are empty. Usually I would now expect that I can fill the submodules using the usual commands “git submodule init” and “git submodule update”.

But it fails with this message:

$ git submodule init
No submodule mapping found in .gitmodules for path 'mxxxxxxx-xxxxxxx'

I believe the reason is that there is no file “.gitmodules” (as you can see in the screenshot). So I am a bit confused now what kind of “submodules” they are.

So please, how can I simply checkout that repository including the submodules? It would be great if someone could help me out with this (probably quite noobish) issue.

Thanks in advance!