I have recently upgraded from 17.04 to 17.10.
Amongst a few things that aren't working any more, the Alt+spacebar combo with a keyboard key (e.g. Alt+spacebar, then x to maximize a window) is not working any more.
I tried changing Settings -> Devices -> Keyboard, since the default Maximize window combo with Super + Up doesn't even work.
This does allow me to set up a working combination of my choice, e.g. Alt + F10, but it's not exactly what I want.
I just want to e.g. maximize a window with Alt+spacebar, then x, as I used to in 17.04.