I can't install this mod because the version of the dependent mod(2.1) required for this mod to work isn't available in the repository.
screenshot https://i.imgur.com/2W7Xbd3.jpeg

Yes - you're right - since the the author of that dependency decided 2 month ago to withdraw the support of 2.1 - see here.

So you have 2 possibilities - you can follow the instructions in that post and use git to get the missing dependency. Or you have to wait, until the other mod will be published with a compatible version for 2.1 - sorry.

Thanks for the quick reply. I'll download it according to the instructions.

Edit:So after unpacking, renaming, and repacking the packages a few times, I managed to install it.
https://i.imgur.com/5iDdHb9.jpeg