The Trinity Trails in and around Fort Worth, Texas, could offer an all-MUP century with some backtracking. It meanders around the city. And in most places there are adjacent paved and light gravel paths, so retracing the route could still be a little different by taking the paved path one way and gravel on the return trip. The "gravel" is mostly finely crushed stuff, what some folks call a "chat" trail, so it's not rough stuff like railroad ballast or chunky rural farm roads.
There are also bike/pedestrian paths throughout Dallas. While there's not yet a contiguous unbroken route from both cities, it'll be finished in a few years. Most folks I know who ride in both cities have picked out a few city street connecting routes that they feel safe doing, especially in groups.