Fixed foveated rendering requires a hack to work. You can't read from the "opaque texture" in shaders, so effects like glass/water refraction won't work. But you can get good looking stuff running at 72fps on Quest.
I am making a custom SRP optimized for use on Quest, as opposed to using Unity's pre-built ones, and had that right eye is black issue too. I think it's a bug from blitting with "BuildinRenderTextureType.CameraTarget" where it only seems to target the left eye. Getting rid of rendering to a texture and blitting it fixes the issue (and will also make FFR work since it is broken with intermediate textures atm too).