What is so specific about "biological" (which is a fairly meaningless term) that can't be replicated if we do the same thing with silicon or other substrates?
I think you are hand waving the whole thing and thinking consciousness = brains.
Sure, our brains produce consciousness, but WHY? Structure? Density of information? Complexity? Brain waves?
Nobody knows.
I believe it is entirely possible that we could eventually create AI that is conscious, or at least, would be able to convince it is. Whether this is achievable is different from whether it is possible, but I do think that if we continue down the current line with LLMs and other models, we'll eventually end up with a system that can articulate its consciousness to the point where the Supreme Court will have to make a decision about AI rights.
Consciousness does not necessarily mean you are non-deterministic in your consciousness operating.
Everything may be deterministic, but too complex for us to figure out at this point.