Agriculture and nomadism/sedentarism

I don’t think a sedentary hunter gatherer society would be very feasible. Although, like you said, small localised examples do exist, any larger society would quickly fall apart. Resources might be abundant in their local area, but as soon as they start to expand they would encounter more average areas, where they would not be able to live. This leads to them being incapable to form economies of scale, and thus fail to see any major technological development.