I want to use Alt+Shift as keyboard layout switcher. The main configuration utility doesn't allow me to do that (it's a default switcher for almost all computer users). Ok, no problem, I can setup it in GNOME Tweak Tool.
But when I press Alt+Shift in e.g. Firefox, it shows me hidden main menu (like if I press single Alt). How can I fix it and make Alt+Shift combination work correctly in all applications?