There is Settings > Keyboard > Layout and there is something called iBus and input methods.

I were using Keyboard > Layout GUI to configure my layouts in 13.10 and it worked fine. But after update to 14.04 something called iBus appeared and now my shortcut Alt+Shift is not working. Looks like something is intercepting this hotkey. If I set hotkey to something else in Keyboard > Layout it's working: I can change my layout, but if I set it to Alt+Shift it's not working at all.

What are those different methods of keyboard input configuration? What method is preferred? How do I enable only one preferred method and disable another one in order to prevent conflicts?

There is iBus icon on the panel. When I click on it, a drop-down menu appears with two input methods. But when I select one of them, nothing happens. The input language is still the same.

Please advise. Thank you!