There isn't. There never was one, because vast majority of websites are actually selfish with respect to data, even when that's entirely pointless. You can see this even here, with how some people complain LLMs made them stop writing their blogs: turns out plenty of people say they write for others to read, but they care more about tracking and controlling the audience.

Anyway, all that means there was never a critical mass of sites large enough for a default bulk data dump discovery to become established. This means even the most well-intentioned scrappers cannot reliably determine if such mechanism exist, and have to scrap per-page anyway.