Switch language on Android device with bluetooth 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 (keyboard app.), this language switch key does not work. Shift + Space does not work either. 

How can I switch language using the bluetooth keyboard?
Go to Settings → Language and Input, then find Languages and select English and your language.
Now you should be able to use Ctrl+Space key combination to change languages from the Bluetooth physical keyboard.