Yes, you can. I have an 2018 Limited with the OEM 18" rims and just two weeks ago went to 15" rims with AT tires (currently no lift kit). The tires I went with are BF Goodrich KO2. Many posts on here from others about similar, or even the same exact set up. Other tires with the same size are available. If you go with 215/75 R15, like I did, then the tire diameter is the same, so no speedo/odemeter mis-measurements. With the '18s, you can go as big as 235/75 R15, which was not possible on the previous model years. Though if you go that big, I believe you'll need a lift kit for sure and still have minor rubbing on the mudflaps. And the speedo/odo will be off a bit, if that matters to you. LP Adventure is a good resource for pics and a various selection of rims (ie. Method, Sparco, etc).
Hope that helps.