It never would have occurred to me to run a RDP server in Linux. It is a proprietary protocol. I would run a different server on a linux machine.

Edit: Thinking back to doing something similar seems like we set up XRDP. I usually just Forward X sessions if I want graphical environments in linux, but I do seem to recall doing it with XRDP too. I think you needed to have a user directory, but they did not have to be logged in.