The Snyder Cut is currently costing millions of dollars to film new scenes for the HBO release, so no, there was no a complete Snyder cut in 2018, not matter what fans and clickbait bloggers say. The theatrical release wasn’t what Snyder wanted, but that was never a secret (just ask Superman’s mustache).
And btw, you guys know what Rise of Skywalker, Justice League, and Batman v Superman for that matter, all had in common? The writer. TROS and the DCEU both reek of classic terrible decision making from Abrams and Snyder respectively, but they both also have the same writer in Chris Terrio. At the end of the day, these movies are bad not because of studio secrets, but because they’re written by someone who has proven to have no skill in writing fantasy franchise blockbusters.
There are surely some deleted scenes for TROS somewhere, though, and fan editors would probably do better with them than an official extended cut would.