From CCP4BB

Thanks to everyone who gave helpful suggestions; I now have stereo working on Ubuntu 18.04.

To help anyone who comes across this in the CCP4 archives in the future, it was necessary to:

1) Install lightdm and set it as the default display manager.  Other display managers that don't do compositing may also work.

2) Install a suitable desktop environment (I used gnome flashback metacity in the end, but XFCE also works).

3) Edit the Xorg configuration (which is now a series of files in /usr/share/X11/xorg.conf.d) to include "Stereo" "10", and "Composite" "Disable".

The step I was missing was the first one.  In Ubuntu 16.04, stereo worked without having to do this.

Thanks again,

Chris
-- 
Dr Chris Richardson :: Sysadmin, structural biology, icr.ac.uk