"# user packages
  nixpkgs.config = {
    allowUnfree = true;
    packageOverrides = pkgs: {
      unstable = import <nixos-unstable> { # pass the nixpkgs config to the unstable alias # to ensure `allowUnfree = true;` is propagated:
        config = config.nixpkgs.config;
      };
    };
  };"