This is probably the same problem as in the DepthNormalsPass, where normals are not outputted on Unlit targets. You probably need to use a Lit shader, doing the “hardcode 0 in everything except emission” trick. But having a “PassFilter” node that will let you output through color, emission, normal outputs, or whatever is needed ONLY in the required passes (Like Meta and DepthNormals)
I think Unity should consider writing this passes whenever the new “KeepLightingVariants” option is checked on the Unlit Master Node if they really want to support custom lighting on ShaderGraph. Its not propper support, but at least will let us have “something” to work with in the meantime