After further research, this seems to actually not be Ruby version specific - because I purged my Ruby 2.5.1 that comes with Ubuntu 18.10 and installed 2.5.3 and 2.4.5 via ([ruby-install](https://github.com/postmodern/ruby-install) and tried both versions - and they both show up with the bug. So, my conclusion must be that there is something else wrong in 18.10, perhaps not Ruby specific at all (but still very odd that it works with Python and openssl directly).
After further research, this seems to actually not be Ruby version specific - because I purged my Ruby 2.5.1 that comes with Ubuntu 18.10 and installed 2.5.3 and 2.4.5 via ([ruby-install](https:/ /github. com/postmodern/ ruby-install) and tried both versions - and they both show up with the bug. So, my conclusion must be that there is something else wrong in 18.10, perhaps not Ruby specific at all (but still very odd that it works with Python and openssl directly).