I have no way of knowing whether other people are conscious except by observing their behavior. Similarly, I have no way of knowing whether a machine is conscious except by observing its behavior. If something is outwardly indistinguishable from an intelligent/conscious/sentient/whatever being and you claim that it's still not i/c/s/w, then you've implicitly accepted the possibility that all humans besides you are not i/c/s/w either.

Your tangent on color vision/hearing/pain is not relevant. None of those things are required for i/c/s/w, nor is it obvious that a machine is incapable of feeling those things.

Also you keep using the term "LLM" a bunch here but I wasn't talking about LLMs. The question of machine intelligence is much broader than whatever the current state of the art happens to be.