I could not hold it anymore and wrote git subgit (useable as yadm subgit, too) which is much easier to use as submodules with 81+ different git projects cloned. It needs a bit more testing and a license.... I will release in a few days.
here is the repository to my new git subgit command, its all work in progress of course https://build.conesphere.com/conesphere/misc/git_subgit
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