IBus binds Super+space to switch the input method engines by default. When users press Super+space, the space char is output and Super+space+space can switch engines in Cinnamon desktop. This does not happen in other desktops. To reproduce: 1. Log into Cinnamon desktop. 2. Run ibus-daemon if it does not. % ibus-daemon --xim & 3. Run ibus-setup and open "Input Method" tab and add more than two IMEs. 4. Press Super+space And then Super+space does not switch IMEs. Expected result: Cinnamon binds "Super" key only but not "Super+space". Super+space can switch IMEs. Workaround: Run cinnamon-settings and select "Applet" -> "Menu" and click "Settings" button. Change the short cut "Super_L" in "Keyboard shortcut to open and close menu" to "<Super>Up".
Sorry fixing this isn't going to happen as I haven't got any more available time to look into this issue.