The second time I made a starter it “took”. Just regular unbleached all purpose flour and water. From there it was smooth sailing, it’s a lot easier than yeasted bread for me. Main things that help:

Always refresh the starter at least twice before making bread with it (so if you want to bake Saturday, refresh Friday morning then make the big starter on Friday night with some of that refreshed starter.)

Refrigerate the dough after it’s shaped. Untill it’s cold or even overnight. This does two things. Makes it possible to do the scoring, and cold dough into a hot closed cast iron pot will create steam that helps it rise.

Which leads to - bake it in a closed hot heavy pot. Commercial ovens can do things home ovens can’t. I do all sorts of baking with the starter but for “the sourdough” as the kids call it, the one that comes out like a $12 Artisan Loaf, baking it enclosed by the hot pan is the trick. I tip the cold dough out onto parchment, score it then use the parchment to carefully move it into the hot pot.

There is a sourdough community on Lemmy, they are a nice group and I’m sure would have more tips but those are mine.