To be honest, no i didn't. But as far as i can determine, i'm not getting far enough in the build process for those bugs to become relevant.

I'm was failing at some very basic level for which i should have known (and tested) the solution after using Linux for 20 years:

$ OPENSSL_PREFIX=/home/cavac/bin/openssl LD_LIBRARY_PATH=/home/cavac/b
+in/openssl/lib:$LD_LIBRARY_PATH perl Makefile.PL 
*** Found OpenSSL-1.1.1a installed in /home/cavac/bin/openssl
*** That's newer than what this module was tested with
    You should consider checking if there is a newer release of this m
+odule
    available. Everything will probably work OK, though.
*** Be sure to use the same compiler and options to compile your OpenS
+SL, perl,
    and Net::SSLeay. Mixing and matching compilers is not supported.
Do you want to run external tests?
[download]

So, LD_LIBRARY_PATH did the trick. Not sure why Net::SSLeay doesn't set it automatically, though...

And now i have to look into testing with the Github version of Net::SSLeay, since the bugs are marked "patched".