Do split flaps produce lift? I don't see how, because there is no change in camber. It seems like an upside down speed break, producing only drag.

A:

Well, after all lift is created by deflecting air downward, which is exactly what a split flap does - although in a very inefficient way i.e. with a lot of drag.

This NACA TN shows how Cl and Cd increase with the deflection δf of the split flap (left plot):