Make sure you're using the graphics card provider's binary drivers. nouvea is only openGL 3.0 and Divinity requires at least 4.0
In a terminal run the following command:
glxinfo | grep "OpenGL version"
If the output doesn't start with OpenGL version string: 4.
then there's your problem. Installing the nvidia binaries is really easy, Read this ubuntu forum:https://help.ubuntu.com/community/BinaryDriverHowto/Nvidia
In short, in a terminal type:
sudo ubuntu-drivers devices
sudo apt-get install nvidia-**
Where ** is replaced with the highest number option your graphics card supports - determined from the .ubuntu-drivers devices command.