Nothing against nixpkgs, but if the user is curious about how things are done in BSD perhaps he should try xbps before nixpkgs. It was written by a former NetBSD committer who wrote some useful programs for NetBSD's userland. I am biased perhaps but I believe it is faster than any other Linux package manager. Always looking for something faster so I am welcome to being proven wrong on that.
https://github.com/void-linux/xbps