I am unable to hear sound from my RPi3B+ running Ubuntu Mate 16.04 when connected to my AV receiver via hdmi with a xrdp connection. Audio works fine in a local session when not using xrdp to connect to the Pi, so I know that there is no problem with the Pi itself. I have confirmed that dtparam=audio=on and hdmi_drive=2 are both enabled in config.txt. FWIW these 2 entries enabled xrdp audio to work on my RPi3B+ running raspbian stretch to work just fine.
This seems to be the only issue I am having running Ubuntu Mate 16.04 on my 3B+. Any additional ideas would be appreciated.