Interesting revelations not many people talked about:
Daisy Ridley confirmed The Last Jedi will have at least some ‘Grey’ in the film and a part of it will have to do with DJ
More signs pointing to this being Ezra Bridger.
Just because Rebels is exploring some of the same themes does not mean there is any connection between the characters. Snoke is more likely to be connected to Palpatine in some way. My personal two theories are that he is either Plagueis or one of those nameless lackies we saw in ROTJ who somehow escaped and took control of one of the splinters of the Empire. Either would be cause for him to hate Luke.