We know how this shit plays out because it's how it has always played out. The haves are going to fight every last penny being taken off them to give to the have-nots. What the social, political and economic elites envisage for the future is not a mass reordering of society centred around egalitarianism, human development, fulfillment and all that hippy nonsense. It's a world much like today except with more technology, where they remain in charge and claim as large a proportion of the societal pie as possible.
There won't be any largesse, because of the same rules apply as now. The world is competition. Welfare is inefficient: if we tax lots and waste money paying for the poor then we'll be less competetive than China / Brazil / etc. and they'll become richer and more powerful than our country. So eat your Soylent Green and live in your 2 metre square box, otherwise you'll speaking Mandarin/Russian and have your media banned by the CCP / Putin-dynasty tsar.
The unemployed masses will be loaded up in accommodation as cheap as possible, with the cheapest, barely-edible food as possible, services as basic as possible, healthcare probably mostly unavailable, with everything as cheap and minimal as possible. With the usual rhetoric about what a bunch of useless wastrels the poor are. And if things get cheaper as you suggest due to AI efficiency, it just means the authorities can the needy less money: the aim, after all, is to give them a minimum standard of living, not a minimum amount of money.
It would be lovely to think people will use their free time to do something interesting and constructive, but a lot of the interesting stuff people want to do needs resources: space, equipment, resources, etc. There'll barely be any, so they'll be locked out of a lot of stuff. It just seems to me that being unemployed is utterly shit now. It's not going to magically be any better with an AI and UBI future.
There is this idea about voting, but in some of our countries, democracy
already seems a little more nominal than actual. I bet you the powers that will be will accelerate that if people do annoying stuff like trying to make their numbers count. If the rise of the global far right, including Trump, tells us anything, it's that you can convince people to vote away their own democracy.