Maybe they are robotic or cyborgs.
So this would be AI, What would the point be of coming here with robots? It would eventually would be to explore land for a biological civilization. Eventually the biological civilization would have to come here unless people eventually get converted into robots, like a RoboCop but perhaps less dramatic. So yes, you thinking a cyborg or robot seems the only likely way
Maybe that's the final level when a planet with intelligent life is ending, sun burns out. I said in my other thread 'intelligence existing on its own" would have to be how this all ends. There simply is not enough scientific research about black holes, time warps and holes, they've been around for years but can never get around traveling past the speed of light. There is this one guy, Victor Wainick who apparently explained it but his work was destroyed.
So eventually the earth ends, the sun burns out. Humanity will likely end before that time. So are we gone when we biologically end? AI may serve as the afterlife, paradise and you exist forever(eternal life) because you'll exist as AI, your sense of humor, memories, everything. You just won't have your body anymore
Stallone is a genius and the Rocky 4 robot looked like most descriptions of Aliens. And it was able to eventually feel. Stallone knew he was limited in the genre, but in Rocky he pursues all sorts of philosophical intellectualism he knows 99% of his audience won't get. In fact when the robot becomes Paulie's "girlfriend" if you listen close it's Talia Shire(Adrians) voice. Burt Young in real life was obsessively in love with Talia Shire.
But I think you are correct, some form of AI would be the most logical explanation for intelligent life visiting us.