There’s lots written about what happened in Finland. From what I can remember it was a success in terms of happiness and fulfilment but not in terms of the economy.
I don't think (also from memory) it was a "failure" economically, just neutral over the length of the study? Mostly in the sense that the participants didn't all rush into employment (which seemed an unrealistic expectation to me given the complex factors involved...).
I do wonder whether over the longer term the improvements to health and well-being would feed into economic activity as well. Plus the economic benefit of people being secure enough to have surplus income to spend.
It does take people a long time to adjust and feel able to fully trust newfound security when they've experienced insecurity. So I'd imagine it could take a while longer than perhaps anticipated before UBI made people feel secure enough to alter their economic activity in any significant way. Especially given that, as I recall, it was trialled with groups who'd faced financial insecurity. (The brain being risk adverse, it learns quickly that something is unsafe/insecure and takes much much longer to adjust to insecurity being replaced with sameness).
Also, the public health angle is valuable and has ripple effects economically. That's why we got a public health service, because having a population in poor health had wider consequences than just for the individuals concerned. It wasn't some generous gift.
I think it goes to the kind of society we want to have and whether we value human life solely for easily measured economic outputs like employment or whether we value the lives people are living and the way we all connect. The distinction between a society that holds disabled people to be an economic burden or inconvenience for having different needs to access employment and one that values disabled people as human beings whose civil rights are beyond question.