Start Xubuntu Session in xrdp

The reason is because several environment variables are not set and passed to startxfce4. Create a /usr/local/bin/start-xubuntu file and put "start-xubuntu" in ~/.xsessions:

#!/bin/bash

export XDG_DATA_DIRS="/usr/share/xfce4:/usr/share/xubuntu:/usr/local/share:/usr/share:/var/lib/snapd/desktop:/usr/share"
export XDG_CONFIG_DIRS="/etc/xdg/xdg-xubuntu:/etc/xdg"

export LANG=en_US.UTF-8
export GDM_LANG=en_US.UTF-8
export DESKTOP_SESSION=xubuntu
export GDMSESSION=xubuntu
export XDG_SESSION_DESKTOP=xubuntu

# propagate to X sessions. It is important when user first
# login, they decide on the initial xfce/xubuntu template settings.
dbus-update-activation-environment --verbose XDG_DATA_DIRS XDG_CONFIG_DIRS DESKTOP_SESSION GDMSESSION XDG_SESSION_DESKTOP

exec startxfce4

Kudos goes to Netspectrum Ubuntu AMI on AWS, which gives you a ready-to-go xubuntu desktop via VNC, RDP or browser in a few seconds.