Are you running stock size tires or have you upgraded?Applied 3M anti-squeak tape to rear tailgate. Virtually invisible. No more constant annoying squeaking coming from the rear hatch (that drove me nuts). Not that one expects a Jeep to be "quiet"... the constant and never-ending squeaking could only be drowned out by the radio (or driving faster than 65). Quite possibly the most sanity saving upgrade I've done.
Picture below with tape applied. Nearly invisible though you can see a few of the air bubbles that should fade with time. Since you won't see it when the tailgate is closed I don't really care.
$20 on Amazon https://www.amazon.com/0-125-5-5430...+5+yard&qid=1556287711&s=gateway&sr=8-1-fkmr0
The squeaking could be a sign of a bigger issue if you have an oversized tire with no tailgate reinforcement. Just don't want you putting a bandaid on and having more problems later on.