After upgrading to Ubuntu 18.04 I discovered quite different trackpoint (stick) and touchpad behaviour, specifically, the trackpoint and touchpad would not work together (however the trackpoint and a mouse would work together).
Dell Precision 7510, upgrading from Ubuntu 16.04 to 18.04.
After much fussing about attempting to configure libinput drivers, the desired behaviour returned by installing the older synaptic driver (Ubuntu 18.04 appears to ship with the new libinput drivers) and rebooting the machine.
libinput drivers:
xserver-xorg-input-libinput
synaptics (deprecated?):
xserver-xorg-input-synaptics
