Population density is the problem/challenge I think more so than absolute population. For cobbled villages, there are farms in Japan that use Yamamoto Transport to move fresh produce across the country overnight, cheaply, and now across Asia overnight too. Can also use it as an inexpensive door-to-door parcel delivery service.

That could also become a robotic service too.

But to really zoom out, as someone else pointed out:

"What would homesteading independence look like in the 21st century in terms of sustainability and so forth?"

I am thinking here about more than just infinite intelligence, but infinite power. Science fact presenting itself as science fiction. And for that you'd need locked-up and hidden technology. Also ways to deal with all the waste and by-products of human evolution. Well said. Supporting the environment that supports us.

So Hub-and-Spoke layouts over Megacities. Providing breathing space for land and people. As much DIY as possible using scalable best-practices with commodity items. Censorship-resistant. Free-flowing funds, energy and information. Protected whistleblowers using a local-first Fediverse that can toggle anonymity on/off. Harnessing waste streams and up-cycling them, and doing the full "Earth shift" while still reaching for the stars!