By the encyclopedia britannica:

"psychological condition defined by the English philosopher John Locke as “the perception of what passes in a man’s own mind.”

So it is impossible to prove that any being outside of oneself has conciousness, unless you compare brain scanners like they did to prove that the color blue is seen the same by everyone (same neural structures lighting up).

But... An LLM clearly can't have consciouness, as its "mind" would be the weights in the model, and the passing through it would be the data going from the input tokens to the output tokens. There is no place for the LLM to detect what is going inside and process it separately.