I would like to know aswell. I think what you would do is make an action button that covers the whole screen with zero opacity and make it that if you press the screen (which basically means you're pressing the action button) and while the button is pressed, the player would go up.
Problem is this. I cant make this movement, where the nose is going up/down like in the picture @Christoph @fez_94
Since this is like flappy, maybe have 2 versions of the character. The static is facing in downward position and the jump is facing up. I know it isn't exactly what you are looking for but could work (sort of).
You can also use the joystick as Christoph mentioned and the rotation mapper. Then as opposed to a flappy type game it would then be an avoidance game and you are using the joystick to move up and down.