Comment 3 for bug 822872

In the meantime, I have found a temporary workaround: in the keyboard layout options (System>Preferences>Keyboard>Layouts>Options…):
1) under “Key to choose 3rd level” check “Left Alt” and “Right Alt”,
2) under “Alt/Win key behavior” select “Left Alt is swapped with left Win”.

The first step solves the problem of also having a comfortable left-hand third-level chooser (left Alt; left Win would have been uncomfortable), so that you may comfortably type right-hand third-level keys. The second step allows you to keep the shortcuts associated with the left Alt key by transferring them over to the left Win key: to close a window, for example, you’ll have to press LeftWin+F4, instead of LeftAlt+F4. As for the Unity launcher/dash shortcut, it is also preserved, but only through the right Win key (no more also through the left one, which now functions as left Alt’s substitute).

I need to highlight that this solution is not ultimate, as a left-hand third level chooser needs to be set in Ubuntu by default, to allow comfortable touch typing (one of the main uses of a computer), as most (European) users would have a hard time figuring out this solution, especially when they’re used to the LeftCtrl+LeftAlt+Key - RightAlt+Key equivalence in Windows.