I don’t buy the latest flagship routers so I’ve never had to set up one without having to create an online account yet. I bet if you look at some Netgear (or similar) models from a couple of years back, they won’t have online activation and they just have the default admin credentials on a sticker under the router.
If you want a more up-to-date one, GL.Inet routers ship with OpenWRT installed, and you don’t need an online account to activate them.