GFCI in a 3-wire sub panel with bonded neutral and ground
A GFCI breaker does not know or care what happens upstream (elsewhere in the subpanel or back at the main panel. All that matters is that neutral and hot are connected to it properly so that it can detect the difference between them. If there is a ground wire going to the protected device then that ground must be separate from neutral until sometime past the GFCI - i.e., whether the ground is connected to the neutral bar in this subpanel is a code &amp; safety issue but won't affect the GFCI.

So the GFCI should not be a problem.

On the other hand, some things look a little strange about the panel. I'm no pro, but:


The right-side breaker 2nd from the bottom looks different. Is it the right type for the panel?


As far as a proper ground path, if your conduit is metal end-to-end then that should give you an easy way to take care of grounding. And if it isn't metal end-to-end, you should be able to fish a ground wire (green or bare copper, size depends on the size of the other sizes) through and then separate neutral and ground in the subpanel.