Universal Basic Income can never happen under Capitalism. It's impossible. Were it to happen, it would literally collapse the system. Unemployment and the threat of such is the engine that keeps people in the wage slavery grind. Take that away and nobody would opt to be a wage slave as opposed to just coast on UBI and enjoy life. And even if not everyone took the UBI route, the remaining workers would have so much bargaining power, they would dictate terms to the bosses, and we can't have that.
Stop thinking UBI has any chance of happening in any large scale.
So get rid of capitalism, the real source of most of our problems. I disagree on your conclusion that UBI can only have one bad outcome, but you're right that the opposition would not allow such a move because it takes away their power. So let's go after the core problem.