 nix repl                                                                                                                                                                                          ~
Welcome to Nix version 2.2.2. Type :? for help.

nix-repl> :l channel:nixos-19.03    
[12.2/12.3 MiB DL] downloading 'https://nixos.org/channels/nixos-19.03/nixexprs.tar.xz'Added 10093 variables.

nix-repl> builtins.tryEval darwin.apple_sdk.frameworks.AVFoundation
{ success = true; value = «derivation «error: Package ‘apple-framework-AVFoundation’ in /nix/store/kq41akzhk1l8413qff7w12jxf1343iwr-nixexprs.tar.xz/pkgs/os-specific/darwin/apple-sdk/default.nix:151 is not supported on ‘x86_64-unknown-linux-gnu’, refusing to evaluate.

a) For `nixos-rebuild` you can set
  { nixpkgs.config.allowUnsupportedSystem = true; }
in configuration.nix to override this.

b) For `nix-env`, `nix-build`, `nix-shell` or any other Nix command you can add
  { allowUnsupportedSystem = true; }
to ~/.config/nixpkgs/config.nix.
»; }