To be able to use XRDP on Ubuntu Linux try the following instructions:

$ sudo apt update
$ sudo apt upgrade
$ sudo apt install xrdp
$ echo “gnome-session –session=ubuntu” > ~/.xsession
$ echo “export DISPLAY=:10.0” > ~/.bash_profile
$ echo “xhost +” > ~/.bash_profile
$ ip a

Remember write down your IP address of your system and to log out of your graphical user session.

Now try to login to your system with a RDP tool.