Hello guys!
I’m trying to change Anchor Presets however press the ALT key and it does not work, it does not change the options …
I have solved the problem of rotating on the object with the ALT key but in Rect Transform does not work.
My Operating System:
Linux Mint 18 ‘Sarah’
Linux 4.4.0-21-generic x86_64
Confirmed, will be fixed in an upcoming build.
Still happens Version 2017.1.2f1
Having same issue still in 2017.2.0f3
Having same issue with Version 5.3.4f1
I had the same problem and I found that Alt + mouse click is bound to “move the window” in Linux Mint. I removed this binding in the system settings and it works now as expected. That means the desktop manager “stole” the click event from the Unity editor. It works in 2017.2 although the version shouldn’t matter.
The setting I did in Mint is: system settings (control center) - windows - Behavior tab - Moving and resizing windows - Special key to move and resize windows : set to disabled.
I am still having this issue under Mint 18.3 with Unity Editor v.2017.3.0p2 . I already had those settings disabled (after having learned of it from another issue altogether unrelated to dev). Neither ALT nor SHFT work. As an aside, I tried on 2 different keyboards just to make sure. I will tinker a bit and see if I can find a workaround. 
EDIT: Referencing this thread seems to indicate that - although there is no feedback - the functionality is indeed implemented. I can confirm this is true. So, until the display gets updated, it will work on Linux, though we may rely more heavily on trial and error than our counterparts. The issue is closed on the official issue tracker entry, though I cross-commented there as well for thoroughness’ sake.
Hope this is helpful to other Linux compatriots.