Switch language with a bluethooth keyboard

I'm using Logitech MK850 bluethooth keyboard and mouse combo on Samsung Galaxy S8+. If I'm using Samsung (default) keyboard, I can switch language (Korean/English) using Kor/Eng switch key on the keyboard (it's actually right Alt key). But I'm using Swiftkey, this language switch key does not work. Shift + Space does not work either.