I don't know cause after the first few modules succeeded I didn't monitor the output of clone-modules nor did I scroll back looking for errors.

Then go back and do it again, and this time keep the output for inspection.

Maybe simply installing one of the "unclonable" modules already fails in a way that allows you to diagnose the problem.

Other people likely solved their problem that way.

My guess is that some of the modules fail because their prerequisites cannot be cloned...

I don't think so because I have the prerequisites. For example Acme::Tools only has few common dependencies. Also Imager itself did get cloned it was only a few image format modules that failed. It's on the same box so I have the SSL stuff that works with 5.38.2.

Imager has no external non-Perl libraries dependencies it needs for installation. Imager::File::PNG needs (for example) the libpng-dev or libpng-headers package installed.

Similarly things hold for the SSL libraries.

Now it's time for you to get your hands dirty and check if you can install those libraries using cpanm (for example), and see if/how they fail there.