The Arbiter

What I'd do here is use seperate standard shaders inside one Karma material node, and layer the shaders using mtlxmix nodes. (I can't double check things, I'm not at my computer.) Then I'd hook up Karma AOV's nodes to the output inside as usual.

However, there may be a problem layering more than 2 shaders together this way from what I've been hearing. So I'm not 100% sure things would work, if I'm misremembering, etc. and can't test it myself at the moment.

Had the same issue myself. Issue was indeed OCIO config related.
Funny enough, Karma CPU gave the correct result in the viewport. Only OpenGL/Vulkan and XPU were off (with XPU being correct when rendering to mplay/disk).