Thank you!
I believe @shanesveller’s pointer regarding propagatedBuildInputs is right (and thanks again for the research!), and just realized that there is a Nix pill on this topic. I’ll try to figure this out, and once I have a solution, I would be happy to contribute to the docs.
Do you track these issues in a public place somewhere? Not very skilled with Nix, but would love to follow along. Or the state of the BEAM ecosystem thread is specifically for that?