I'm using RPI3, Ubuntu Mate 16.04 and PiCamera V2. All is working well.
While using VNC - I don't get any stream view ( raspivid, raspistill and Python ).
Is there a way to config PiCamera or VNC to be able to do so ? Guy
Yes. You need to turn on the direct capture mode in the VNC server on the RPi.
To turn this feature on, open the VNC Server dialog (on the RPi), navigate to Menu > Options > Troubleshooting, and select Enable experimental direct capture mode.
The link above gives more details.