It has been sometime since the last update for Linux. I understand that you are moving to a native "3DCoat" build under newest Ubuntu using its latest "GCC". This is taking sometime to get to that point. Is there a expect date on this completion.
On start-up "3DCoat for Linux" automatically enables tablets which it is able to recognize. Otherwise the tablet should be enabled manually by defining the environment variable "COAT_PEN" equals the name of the input stylus device. For example: export COAT_PEN="Wacom Intuos3 4x6 Pen stylus"
Since "3DCoat 4.9.70 for Linux" it outputs into the Terminal the list of your input devices. Please see the attached screenshot as an example. You have to send a screenshot with the name of your input stylu