We still have no idea what mechanism causes consciousness. I bet in 25 years we'll be no closer to understanding it than we are today. I think this is a good lesson for those watching LLMs and thinking we're on the cusp of imminent AGI.
Depending on the definition of AGI you are using, you don’t need consciousness for it. I think most do not require it as of now. Also; ‘it’ will know it has consciousness when it has it, arrogant humans will still deny it.
edit: mainstream science at times has denied that babies, black people, and animals feel pain. Instead, it has suggested that when injured, they behave in a way that causes (white) people to project their own pain onto them; i.e. they anthropomorphize. I mention this to point out that even the analogy to other humans fails when they look a little bit different.