Nobody does and anyone claiming otherwise should be taken with cautious scrutiny. There are compelling arguments which disprove common theses, but the field is essentially stuck in metaphysics and philosophy of science still. There are plenty of relevant discoveries from neighboring fields. Just nothing definitive about what consciousness is, how it works, or why it happens.

Yeah, and until it can be identified, saying that a LLM treat printer is surely approaching sentience is pure marketing hype.

Nobody does, we might not even be. But it's pretty easy to guess inorganic material on earth isn't.