Look at Poland since 2015. We don't have UBI per se, but we have uncoditional handouts of free money to families with children, which goes to about 4 millions of families (so, like half of them).
And while the programme is not universal nor the handouts are very big (around $200 per child per month) the costs are astronomical and it’s already driven inflation in the country (along with other social programs). I can’t imagine what would happen to economy if this was expanded.