Seems to me this is begging the question. Like, you are asking for speculative fiction so there are no wrong answers. But here you go:

First, society would stagnate because all intellectual work will be done by LLMs which only know how to do things the way we always have. So progress comes to a halt. Profits inevitably stop rising as 30% of humanity no longer consumes whatever it is people working are making.

Those 30% will have to just create their own society. Maybe it looks like Mad Max with the outsiders raiding cities for food and supplies, or maybe they take over a bunch of arable land and just live.

More and more people are pushed outside of the city-states of the rich until it's just them hooked up to VR goggles and nutrition IVs and jerking off into virtual swimming pools of gold at a virtual Epstein island, living their dream, unaware that they are irrelevant and unmissed.

Everyone else carries on without them, and any time someone gets too rich or powerful they are promoted/exiled to go live in the gilded prison of the rich.