For most dev libraries I use

https://github.com/nix-community/home-manager

Which manages

https://github.com/jdx/mise

Which manages uv and pyenv and stuff for python, and package managers for just about every other language I dev in.

It’s version managers all the way down lol, but it’s the only way I’ve found to have proper declarative versions within my nix config that don’t rely on the nixpkgs ecosystem changing, and doesn’t require manually managing a package manager for every single language I use