I have this exact problem, only I'm using the Windows version. I do get an initial input variance total, but even after I run GBDeflicker I get no output variance, nor do I get a luminance graph.
When I run GBD, I do notice *some* difference in the before/after footage, but the biggest effect is that the darker frames get milky. Not exactly the "correction" I was looking for....
Does anyone have any advice?