nixos-server-conf/shared/ssh.nix

{ config, lib, pkgs, modulesPath, ... }:
{
    services = {
        endlessh = {
            enable = true;
            port = 22;
        };

        openssh = {
            enable = true;
            ports = [ 23 ];
            settings = {
                AllowUsers = [ "dev" ];
            };
        };
    };
}