What material is my waste stack made of, and what can I do with it?
The black is Orangeburg pipe, a layered (tar-based?) pipe. I did not think it was allowed inside, I have only ever found it as vents not as drains inside , yes it should be replaced with plastic , it usually falls apart in ground but your’s looks to be in good shape, (that could be ready to fail) , yes replace it if doing any remodeling before it breaks. Tapping with a mallet can break it you will see when you start taking it apart. I have seen remnants inside but not in use I should say.