Мне нравится использовать этот Бесплатный Инструмент тестирования HTTP-заголовков, чтобы отправить, добраться и пользовательские HTTP-заголовки
Use an external dynamic DNS service to associate your IP with a DNS name.
Then, you can port-forward different external ports to the same RDP port on different internal systems. This is not routing, this is just one of the many ways you can use the features of NAT.
The desktops, of course, will need to be on, and have static internal IP addresses, or else the port-forwarding won't work.