This is the home-manager configuration I'm using on my laptop which runs Nixos 20.03. I'm only using 20.03 nixos and home-manager channels, so you don't need unstable in order to use these files.
New polybar theme and shell config: Old theme:
cd ~
git clone https://github.com/Th0rgal/nix-home ./configs/nixpkgs
home-manager switch