To begin a sourdough starter, do I use regular flour and then feed it with Rye?

Whole (dark) rye flour is an excellent way to get a sourdough culture started. It usually has wild yeast already present and has more nutrition for the culture so it gets things moving along faster. I started with 100% rye flour and elaborated two cultures by slowly adding increased amounts of wheat flour to one until it is now all wheat-fed. I maintain both rye and wheat sour cultures for each type of bread although it probably isn't strictly necessary.

Hi there! I'll admit I'm not a bread expert, but I don't think you necessarily need to use rye flour on your sourdough starter (you can continue to feed it with all-purpose). That being said, you can introduce rye flour into your sourdough starter, though you'll want to wait at least a week until its bubbling and growing. I hope that helps!