Question Severe Banding that looks like 6-bit color w/ post stack v2

OK, so I have been trying to figure this out for days now. I've searched multiple times for answers and finally boiled it down all I can to where I know this is something about the post-processing stack. Doesn't matter if I disable all the volumes, the only thing that fixes it is if I turn off post-processing entirely. Thing is though, I want to have it on. That's why I installed it, duh!

Here is the scene view w/o the effects icon turned on (skybox, fog, etc) which includes post fx, same thing will happen if you disable under Rendering on camera from game view.



Looks decent. But then if I turn on that icon (top right in the image) this will happen:




Like, seriously what gives? That looks like you put it through a bad toon filter or some crazy bit depth reduction effect. Is there something I'm missing? I've tried checking HDR in the quality, setting the HDR dropdown in the camera to Use Quality, and a bunch of other nonsense. Is there some way you're supposed to change the exposure of the scene when it's rendered instead of in post or something? Because that's all I can think of.

 

https://github.com/keijiro/unity-dither4444