Since I’m using blender with 3Button-Emulation (really can’t stand using the middle-button for rotation) I’m heayliy using ALT+Left-Mousebtn. There is always a problem with Linux/Gnome/Ubuntu/whatever.
To make the long story short. Using ubuntu-mate it is quite simple:
System->Preferences->Windows->Behaviour->Movement Key: Check Super instead of Alt
Beforehand I tried all kinds of ways for gnome/compiz… Not sure if that did have any effect: