For what it's worth, I have a 2019 Rebel with close to 50,000 miles on the odometer. At around 40,000 miles I could not stand the road noise of Stock Duratrac tires. I came across a sale at the local Costco and pulled the trigger on a set of BFG KO2s. The KO2 solved the road noise issue, though the KO2 made the Rebel ride a bit bumpier (I have the coil suspension), but were also sturdier at highway speed than the floaty feel of the duratracs.
To my surprise, the gas mileage got worse. The truck went from 17-17.5 MPG to 15.5-16 MPG. The Rebel is all stock with stock-sized tires. I initially thought it would get better over time as the KO2 wore in, but with around 10K on the tires, MPG is still in the 15.5-16 MPG range. I realize now that the added weight of the KO2 at each corner compared to the lighter weight of the duratracs that comes stock on the truck is likely the culprit.