What to do if Reshade doesn't find the Depthbuffer?

So, I've had this happen many times, especially with older games: I try to setup some nice SSAO through Reshade, but the effect simply doesn't work. If I enable the "DisplayDepth"-filter, my whole screen turns completely white, which I interpret as "there is no depthbuffer", which is likely the explanation for why SSAO doesn't work. Going to the advanced options, I see a check-box that apparently performs automatic depthbuffer detection. I am guessing that this does not work with older rendering backends (old OpenGL or Direct3D).

So the question is, is there any way to make the depth buffer accessible to Reshade for these games by providing some custom accessor or something? How would that work?

Recent examples with this problem were: Arx Libertatis, Freelancer.

Go to the add-ons tab and experiment with the options of the Generic Depth add-on to find it.