Thanks to additional information as to where to find these packages, I was able to correctly install zef after reinstalling rakudo. Apparently, even the rakudo package cannot be installed on Ubuntu 22.04 using the typical apt-get method, but when installed from the obscure site linked above (i.e. https://nxadm.github.io/rakudo-pkg/), zef can then also be installed and function correctly. Following this, I was able to install DBIish, but have had other demands on my time since then that have so far prevented me from testing the setup further. I believe, however, that the way forward now has a green light, and I thank you very much for providing this answer.

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           (O)    (O)   {▒▒} \_____/ {▒▒}   (O)    (O)
                           O|OOo|oOO|O 

Ready to fly again!