I have made a couple of attempts at sourdough waffles over the past month. In the first one, I had a problem with my homemade buttermilk. But now, after trying this second batch, I think that the homemade buttermilk is only half of the problem. To try and avoid the issue of buttermilk, I tried this recipe (I set it up last night and made the waffles this morning). Like the last batch, these waffles had a strongly sour almost vinegary taste. I realized that the main problem is my starter because I did not have the same problem with my original batch of sourdough pancakes.
So, I realized that instead of using unfed "discard" starter (i.e. the starter I should discard before feeding in order to keep the wild yeast young and fresh), I should use young starter made in the manner of the Tartine Bread (i.e. a tablespoon of mature starter in a mix of flour and water let to mature until it smells like fruit and floats in water) or similar. I will try again!