Switch to openssh_hpn

modules/common/default.nix

···
     ./locale/en_US.nix
 
     ./network/firewall.nix
+    ./network/ssh.nix
 
     ./system/coreutils.nix
     ./system/firmware.nix

modules/common/network/ssh.nix

···
+{ pkgs, ... }:
+
+{
+  programs.ssh = {
+    package = pkgs.openssh_hpn;
+  };
+}