I keep forgetting that UBI, implemented properly as you describe, in a nation with pre-existing Robin-Hooding ... is a net-gain for liberty.
Yet, given history, I doubt that the median-minus-one politician could have the courage to end the current welfare programs if and when a UBI system is enacted. So I'm ... ambivalent ... about what to think of UBI.
Since you probably can't implement a sufficient UBI to provide an income
floor that removes the need for other programs initially (at least, anytime soon), but instead need to start low and ramp up with productivity gains, you need a phase-in mechanism.
You can do this in a way that avoids forcing politicians to have the will to eliminate existing means tested programs but achieve that in effect by simply, add party of the phase in, specifying that UBI income counts as income in applying benefit formulas for existing programs.
It'll be much easier to kill each of the programs when no one has a low enough income to qualify for it.
Yet, given history, I doubt that the median-minus-one politician could have the courage to end the current welfare programs if and when a UBI system is enacted. So I'm ... ambivalent ... about what to think of UBI.