All available information is for ancient versions, so here specifically for 16.04:
Is it possible to remote in via a MSWindows PC with mstsc.exe to a Ubuntu 16.04 PC running xrdp without the need to install an alternate desktop?
This is broken since 12.04, so any update here would be appreciated.
Updated information
It's possible to use XRDP IN conjunction with Unity Desktop in Ubuntu 16.04....Please read full instruction at http://c-nergy.be/blog/?p=9962 You will basically need to perform the following actions
and you are good to go....
If you are still using the vnc4server or x11vncserver, you can also use a quick and dirty workaround (explained here) . Basically, you will install a vncserver on your Ubuntu machine and the xrdp package software. When connecting to your ubuntu machine via the remote desktop, you will select the connect to console option and you will see your Unity Desktop. In this case, you basically using the xRDP as a proxy server that allows you to access your desktop through VNC protocol
Note : Some people mentioned that there might be a need to check firewall status. If firewall software is running on the Ubuntu machine where xRDP is installed, you might need to open the appropriate ports (i.e. 3389)
Hope this help