My AMD Radeon graphic card is not working on 16.04
Solution 1:
To tell if your card is working, do a xrandr --listproviders. Both cards should be visible.
If you want to use it, the best way is xrandr --setprovideroffloadsink radeon Intel, with it, you can use your discrete card for the applications who need it the most (for example games, 3D modellers...) by prepending the DRI_PRIME=1 environment variable:
DRI_PRIME=1 glxinfo | grep "OpenGL renderer" should give an output of OpenGL renderer string: Gallium 0.4 on AMD <platform>.