But nobody disputes that the physical substrate (e.g. brain) is necessary for consciousness. The question is whether it metaphysically suffices.

Actually, you are mistaken.

Professional philosophers may think that way, but dualists who are my neighbors and probably yours do not. They believe, for example, that the spirit (soul, consciousness, call it what you will) survives the death of the body. They do not believe that people with brain damage have lost their consciousness, but rather that their spirit/soul is just trapped in their bodies and unable to communicate to the outside world. They do not think that people with serious mental disabilities caused by the brain have any less of a "soul" than those of us with healthy brains; again the trapped in the body analogy is apt. Most "average joe" dualists do not think that consciousness depends upon brain function in any real or tangible way.

We see colors: the redness of red, the greenness of green. We hear tones, sharp or high-pitched or dull or low. We taste flavors, salty or bitter or sweet. We feel emotions like joy, anger, or sadness. Zombies, by contrast, have none of these experiences.

Neither did I after a few days on Zyrtec!

lets say there is a conceivable world with a bridging law such that the equivalent of a "zombie" created in our world (not a p-zombie by Richard's definition) has qualia. An identical Richard in that world refers to that zombie in this world is a p-zombie while Richard here refers to the same zombie as not a p-zombie.

as to disproving qualia, one can easily be lead on a wild goose chase - note that qualia are a effect not a cause and are vaguely defined. If you want to disprove such an idea you must either find an effect that contradicts our understanding of the world (but it has no physical effects) or prove an internal contradiction (which would require some detail on the nature of qualia).

But nobody disputes that the physical substrate (e.g. brain) is necessary for consciousness. The question is whether it metaphysically suffices. Perhaps, as dualists contend, the brain gives rise to consciousness only because of certain extra-physical background conditions (e.g. psycho-physical bridging laws) that could have been absent.

(So, ironically, it's the very fact that you have some empirical grounds for thinking them non-conscious 'zombies' which guarantees that the attribution doesn't quite fit.)

For example, one person could not "see" an item that was thrown at them on the left side of their body. But they caught the item every time, preventing themselves from being injured, showing that they did actually see the item, but they were unaware of seeing it. In a sense, they were acting just like a zombie in this scenario. They had no qualia or consciousness of sensory input regarding the left side of their body, but the actually sensory input was there and working perfectly, even to the extent that it created the desired outcome: preventing injury.