Honestly, I think it would even be acceptable to punish UBI "freeloaders" with, like, austerity. Like they get slow(ish) internet, a 10x10 foot studio apartment with a toilet, a stand-up shower, a counter with a mini-fridge and a hotplate (or premade food rations, whichever is cheaper), and a single window with a shitty view. Nutritious food, clean water.
And then, if you have proof of another habitable residence, you can get the cash value of all that instead.
The tricky part is that the austerity absolutely cannot reduce anyone below the minimum actual needs to live a full human life. You absolutely need to be giving them enough and healthy enough food, and water. The apartment can be claustrophobic, but it needs ventilation and sound insulation so people can actually sleep. The bed can be boring, but tall people can't be literally cramped when they sleep, and it needs to actually support their weight so people don't get back injuries. Health care needs to be fully adequate. Basically, minimum needs are 100% covered, so that if anyone ever wants to get working they don't have any immediate barriers. Don't take away anything that will make it harder for people to work.
There are many who would feel blessed with a 10x10 studio apartment with a (safe, clean, minimal) bathroom in the corner and barely enough room for good sleep, with shitty Internet and a bad view, and a barely-functional kitchen (and heat when needed, and maybe even cooling when needed).
(I've stayed in cheap-ish hotel rooms that are a lot larger and more flexible than that. I've also stayed in far worse.)
And that's... well, fuck: Isn't that OK? Is it not OK for some people who have (for whatever reason) failed to thrive and climb ahead at the present time to have these things?
(I think it's OK to give all people means with which to limit how far they can fall, even if that means that many quasi-successful people are essentially including this as a line-item that they pay to themselves on their own tax bill.
I also think that it is imperfect, and that we mustn't let imperfection stand in the way of general progress.
I mean: Nothing is fucking perfect. But the mere existence of ubiquitous imperfection doesn't somehow mean that positive progress cannot ever be made.)