Some results are, however, relevant when assessing them from the world of (post-pandemic) 2020: the participants of the experiment reported 1) less economic troubles and financial stress; 2) Higher confidence in future possibilities; 3) More self-determination and autonomy.
The entire point of UBI is to secure everyones basic human needs, not get them a job (unlike unemployment benefits).
If we were to test UBI also on employed people, and observed their behavior, we might avtually gain useful insight into mechanica with UBI. Perhaps we will see more 6-hour workdays with more people employed?
The important gain would be to give people breathingroom to actually find a job most relevant to their education and skills instead of just jumping on the first available opening to be able to pay the rent. Or even spending some time improving your skills.
In the US I think just introducing universal healthcare would accomplish part of the same thing.
Given that it significantly improved mental health, it seems reasonable to expect that this UBI model would lead to some savings in public health expenditure. Arguably there should also be some savings compared to the administration of the current unemployment benefits that require the person to provide evidence of activity and other such things.
How well it compares in practice to the cash cost nobody knows as the experiments are all too short to really tell.
Do we really need to test that though? It seems obvious that giving someone money without affecting their taxes, the price of goods etc would do this.
The issue is that once you roll it out on the society level, it's not the same any more. It will affect their taxes and inflation. Will they still report less economic troubles and financial stress when they receive $500 a month but their rent has gone up by $500?
Checkout the auto complete in DDG or Google for "welfare causes ...". Look at the arguments in the results.
We can't even have the discussion that you say is "the issue" because society is still stuck at the part you claim is obvious.
It's rather secondary to the real objection to UBI: paying for it.
I'm saying BOTH that it's good for people AND that it's affordable are still in dispute and that the claims are clearly not obvious.
The arguments - with varying degreees of plausibility - are all of the form 'long term welfare dependency is unhealthy for society' not, 'welfare recipients would be happier if their welfare income was lower'.
And that's not conflicting with reporting less financial stress during an intervention. The self-reported consequences from eating some candy are very different from the consequences of using candy as a primary diet for long periods of time.
If you won $1bn in the lottery, you'd be quite rich and, in so far that money can make you happy, probably also quite happy. If literally everybody won the lottery at the same time and got $1bn, you'd be back where you were before winning the lottery, as your $1bn wouldn't have the same relative value. Sure, you have a billion, but bread now costs $100k and your rent is $100m.
I happen to believe they are but this study doesn't establish that; and we are missing a golden opportunity to do some real UBI studies with the billions in aid that are suddenly sloshing around.