... “Hard times give birth to strong people, strong people create easy times. Easy times create weak people.”
As of now we are in the stage where it's easy times and people are weak or at least in some other parts of the world. In middle east or in far east, where people are working in a mine digging coals and catching fishes and she'll to eat, they are pretty strong that they may survive even if the world goes back to dark ages.
The UBI must be intended to those weak people these days.
I'll give you a cynical but pragmatic opinion:
1. Weak “people” should be supported by relatives, so that everyone understands that you can't leave “weak relatives” on the shoulders of others who pay taxes. This category includes pensioners, people with disabilities, etc. groups of people. The state has no money other than the taxes paid by all other citizens.
2. There are pension savings and state pensions. Yes, their level should correspond to the minimum necessary income for a person to realize the minimum necessary needs. But pensions should also be proportional to a person's contribution to society.
Why is all this necessary? Because as soon as it turns out that you can do nothing and live a quality life, many people will take advantage of it, and first of all it will lead to the migration of lazy people from other countries, and this will lead to rapid degradation of the social system of the state, the destruction of the economy, and other negative consequences.... And then it will become hard for ALL.