Months ago, in 2019, I watched a YouTube video where a guy talked about this coming book and he said the book would come out in March of 2020 and he talked about how the Emperor created a wormhole and went through to escape death on the second death star at the end of Star Wars: Return of the Jedi. He teleported through the wormhole to a planet that had a lot of dark side energy of the force. And there, he died or began dying. But the dark side was there, many Sith spirits somehow entered his body to revive him. So, according to the video from like December of 2019 or earlier, there was no mention of clones as far as I remember. Not to say that the video was accurate but I like what I heard in that video because I like wormholes and that would probably be the best way for Palpatine to escape that quickly.