Somewhere between jellyfish and mouse, because there lies the level of neural connectivity required for neural processes to observe and predict the interactions between other high level neural processes, to integrate the information about the "self".

So if it's about the level of sophistication of the machinery, and the conscious machinery arose out of matter that was not previously considered conscious, why does it matter if it's organic neurons or silicon?

In other words, if conciousness arose somewhere between a jellyfish and a mouse, why can't the same be said between a perceptron and an LLM?

It can be said, but whether it is true requires that the invariants of consciousness are satisfied by the LLM. Until those in variants are well defined any such claim will be subjective at best.