If you’re okay with ibus-hangul, you can configure the keyroard shortcut for Gram.

Click “Add” and press “한/영” key on the keyboard.

ibus

​All Korean keyboards, including the one on my LG Gram (which is a Korean model), have a dedicated key for switching between English and Korean (the “한영키”). Everyone who isn’t technically inclined uses this key. Using Ctrl + Space is a bad user experience.