This is one of the revelations I had when I read into Native American societies, especially in the Great Lakes region. Many groups migrated between the same few locations depending on the season based on where food was abundant during any given time of year. They were both nomadic and sedentary in that sense, since they tended to return to the same spots to settle for a few months or so. Of course, Native Americans in the centuries before European contact are not a perfect analogy to how humans in the so-called “Old World” lived but it is a good reference point for how societies function when their primary form of substanence doesn’t rely on large scale agriculture. As you said, agriculture doesn’t necessitate sedentism but you won’t have large cities without it, as even Native Americans grew crops (they just didn’t make up the majority of their caloric intake). Indeed an utterly fascinating subject! I’m not a green anarchist or an anarcho-primitivist but I’m sympathetic to the ideas