When I run my sourdough bread baking courses, I often get asked criptical questions from my curious students. The answers to some of the questions like: 'Is sourdough bread gluten free ?' initially seem very obvious, but strangely enough when you dig a little deeper the answer is not that clear cut.
So, first of all to satisfy your curiosity to know whether sourdough bread is gluten free, well, of course it depends on what type of flour you use! Since it's very difficult to bake a true sourdough bread from completely gluten free flour, traditional sourdough breads are not gluten free.