Rye, barley, and certain amaranth species are better suited for brutal climates and inferior soils. Tibet mainly grows a strain of barley adapted to the poor agricultural conditions, AFAIK.
You can process almost any powdered food item flour into something resembling bread, if you expend enough effort on it. You can make bread with cricket flour. Even meatloaf could be considered a type of "bread", if you massage the definitions long enough.
But I'd guess that Tibetans mainly eat barley bread. Rye and barley aren't as good as wheat is for making leavened breads, but they can make a loaf that isn't entirely brick-like, if the baker keeps a good sourdough starter and it gets a lot more rise time.
You can process almost any powdered food item flour into something resembling bread, if you expend enough effort on it. You can make bread with cricket flour. Even meatloaf could be considered a type of "bread", if you massage the definitions long enough.
But I'd guess that Tibetans mainly eat barley bread. Rye and barley aren't as good as wheat is for making leavened breads, but they can make a loaf that isn't entirely brick-like, if the baker keeps a good sourdough starter and it gets a lot more rise time.