Problems with Home Manager

It’s fine. Next time please read carefully the documentation, it’s among the first sentences of the relevant paragraph: Home Manager Manual

“My changes aren’t taking effect (and it turns out it’s not running my code)” is universal; I’ve often run into that. – “Check it’s used/read” is a neat troubleshooting trick to keep in mind to mitigate frustration from such mistakes.

FWIW, the info box in the manual (just further up from that link) also says ~/.config/nixpkgs still works for home.nix: