NixOS had some problems particularly the llvm and clang compilers that complained a lot about missing standard libraries and headers.

I think it’s likely that you’re trying to just add clang/llvm toolchains to your development shell like this:

pkgs.mkShell { packages = [
  llvmPackages_16.clang
]; };

But you actually want something like:

(mkShell.override { inherit (llvmPackages_16) stdenv; }) {
  packages = [ ];
}

Open firmware is important for trusting your boot chain. Seeing their list of partners in the article makes it look like a bunch of cloud providers want to take early boot security very seriously.