nix-shared/system/default/ssh-authorized-keys.nix

{ config, ... }:
let
  primaryUser = config.system.primaryUser or "tb";

  ssh_key_tb1 = "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIBW//dhztkY2OJTXK/1tpOdithfSX4tXt3w5CKPJPfFm tb1@ubi";
in
{
  # Allow root login with `tb1` ssh key.
  users.users.root = {
    openssh.authorizedKeys.keys = [
      ssh_key_tb1
    ];
  };

  # Allow primary user login with `tb1` ssh key.
  users.users."${primaryUser}" = {
    openssh.authorizedKeys.keys = [
      ssh_key_tb1
    ];
  };
}