The method of switching between keyboards on the iOS platform has always left a lot to be desired. Tapping on the tiny Emoji/language button at the bottom-left-hand side of the keyboard is nothing short of tedious, especially if you have larger fingers, but it doesn’t need to be.
KeySwipe (iOS 11) is a free jailbreak tweak by iOS developers Delewhopper and Julio Verne that lets you switch between keyboards on demand with a swipe (up or down) on the keyboard interface. As you might come to expect, this also means you don’t need to fiddle with the tiny Emoji/language button on the keyboard anymore.