I'll tell you right now you're gonna get a bunch of liars. You can't approach this level of modern tech for $250 in a vintage bike. I got an 80s Schwinn Voyageur frameset for $50, but to add STI shifting, tubeless wheels, tubeless tires, and all the little bits to make it work cost waaaaay more than $250. But, I'll admit that my Schwinn is a million times better than that walmart bike. I can't believe there is only one set of bottle bosses, and a.. freewheel? Ugh, gross.

Edit: My point, it sure seems like a great way for the masses to get into the gravel game, but it's not an off the shelf replacement for a real gravel bike.