Which antenna do you have? The crank up batwing? (If so there is a
HDTV replacement kit (Camping World) that you can get to just replace the top (and not mess with the roof.) I would think that a 2018 wouldn't have the batwing.
If you already have an HDTV antenna I can't really help as I haven't looked for anything better than that (ours still has the crank up batwing).
If you watch a lot of TV you might want to sign up for a streaming service--then you don't need a TV antenna at all (just decent WiFi/internet bandwidth).