> IOW if we don't know what consciousness is, how can we call LLMs conscious when we haven't seen even the barest intermediary steps towards our nascent concept of consciousness first?

We stipulate that other human beings are conscious from their behavior and how it relates to ours when it is accompanied by our personal introspective experience or "awareness" of being conscious during normal cognition. The process for ascribing consciousness to LLMs would be same: A stipulation on the basis of behavior that relates to our own behavior and how it appears to be linked to the introspective experience of being conscious.