Would that UBI (as is often said) replace all forms of welfare, unemployment benefits, special subsidies, etc?

Short-term unemployment insurance would still exist, as would special, largely in-kind support for children in poor families (free lunches in school, protective services etc.) Much of the rest could be replaced.

It doesn't look like it will end poverty

It makes sure that the very poor aren't altogether dependent on the labor market for their survival. This is a meaningful improvement in their condition - perhaps the only possible one, given that poverty in the U.S. is in fact quite materially luxurious compared to, say, middle-class life in Namibia.

Essentially it's the per-capita expenses of running a concentration-camp in the tropics when you don't care much about life-expectancy, never mind quality

Of course, and I said as much, but the interesting question is what you need to add to that in order to really satisfy people's 'basic needs' in a reasonably objective sense - and in a way that's sustainable in the long term. Many people in poor and undeveloped countries manage to adjust to remarkably low living standards, and are nonetheless quite satisfied with their lives. So material deprivation is clearly not an issue for them at least.

And here is John Cochrane discussing Murray's proposal

He raises some good points, but I think he overestimates the political unfeasibility of the whole thing. Market-based policy reforms have worked quite well in the past, and they might work here too, especially with 'bi-partisan' support. He also wants to make people go through a purposefully uncomfortable process in order to keep qualifying for the "benefit", which is a terrible idea. High-income people will be offsetting the UBI with their taxes anyway; they're not the problem as Cochrane implies.