{...}: {
  users.mutableUsers = false;
  users.users.root.openssh.authorizedKeys.keys = [
    "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAINTvwXCT99s1EwOCeGQ28jyCAH/RBoLZza9k5I7wWdEu"
  ];
}