I liked the fact that one of the examples given for an “anarchy” was medieval Iceland.
A remote island that nobody had any particular reason to attack. Though if I remember correctly, the Barbary pirates raided the island at least a couple of times.
IOW, an anarchic settled society can survive fairly well as long as there are no outside threats. If there are, the society needs to be organized to resist it, which promptly leads to development of a chiefdom or state. Any society that doesn’t evolve in this way is promptly overrun and destroyed by neighbors who do.
Another example of an anarchic society given upthread, though IMO an inappropriate one, is traditional Irish society.
Which ties right into my previous comment. Irish society appears to have been utterly incapable of uniting against an external threat, perhaps largely because of its anarchic tendencies. Once the Vikings and then the English moved in, the Irish were never able to organize effective national resistance, leading of course to their eventual conquest and subjugation.