I'm using CentOS for my mining rig but I would expect that it is similar for Ubuntu. The rig consists of 4 GTX1060 6GB and 4 RX480 4GB.
*) The NVIDIA cards didn't make any problem and it was easy to OC them with nvidia-settings. (I get about 25 Mh).
*) In order to get the expected 30Mh for the AMD cards I had to patch the kernel module. This is definitively a bit more complicated than in Windows