Again, in what regard does the barbarian class ever refer to tribes and such ? It just doesnt. D&D Barbarians can origin from cities, or civilization as a whole, just fine.
Which I think just sums up the baffling incoherent confusion of this class. What even are you talking about? Warriors who have supernatural rage coming from animalistic shamanism can come from civilization just fine? What? How does growing up on streets give you the ability to channel the spirits of bears and elks? Shouldn't you maybe know what an elk is first? Doesn't the very word barbarian mean they are not from a city?
Why not just have an option where fighters can have rage? That is all this should be. A fighter subclass called berserkers who learn how to channel raw anger.
Barbarians can come from cities. Amazing. Next you will tell me vampires are big blood donors and elves mine for gems underground to.
Now granted anything can happen just fine in D&D so long as that is what the DM wants to do. You want all the barbarians to only come from cities? Fine. But we are talking about a character invented by Larian to represent this class. If we are going to have Barbarians mean street wise muscle then explain that in the background and make the mechanics make sense.