You can already see this in countries with less extreme difference in the society's economy, e.g. Scandinavian countries. They do not have UBI (yet) but have g

You can already see this in countries with less extreme difference in the society's economy, e.g. Scandinavian countries. They do not have UBI (yet) but have generous benefits for unemployment, sick pay, disabilities and pseudo minimum pay so that most people earn a decent income. I am not an economist or sociologist but the economy still works, most people still work and it has lead to 2) and 3). There is less interest in the less desirable jobs so their salary has subsequently increased. And there is heavy investment in automation, in farms, in manufacturing, in shops, etc. It is not perfect though. Maybe UBI will be even better.