For Ubuntu 18.04 Bionic, this works:
sudo apt-get install xorgxrdp-hwe-18.04
This installs a compatible xrdp package
The old version is not compatible and if you have it installed you
have to:
sudo apt-get install xserver-xorg-core
sudo apt-get -y install xserver-xorg-input-all
This removes the old stuff if you have it installed
DON'T USE THE SOLUTION BELOW!!!!
Also other answers on the internet suggest this solution that just adds another issue to your Ubuntu 18 install
Xrdp shows a blank screen with Ubuntu 18.04, Bionic Beaver
To solve this "second session" problem and allow as many sessions as you need, edit /etc/xrdp/startwm.sh and add these lines before the lines that test and execute Xsession. The $HOME/.profile is not part of the solution, but is something that should be run before starting the session anyway.
unset DBUS_SESSION_BUS_ADDRESS
unset XDG_RUNTIME_DIR
xorgxrdp-hwe-18.04
on 18.04.05 it says: Depends:xorg-video-abi-24
andxserver-xorg-core-hwe-18.04 (>= 2:1.18.99.901)
– Gabriel Fair Jan 10 '21 at 16:03