The Guardian is an openly biased (conservative) publication, and they make no claims at being a "news" source. So you kind of have to take their stories with a grain of salt, understanding that they're selling an agenda. They're like the PR arm of the Heritage Foundation, a conservative "thinktank" and lobbying group that pushes Reagan-era economic and social policies that are widely considered primitive and regressive today. edit: I'm apparently confusing my news sources.
For example, this article claims that that various UBI schemes "don't work" and then uses a variety of arbitrary metrics to determine what "works" and what doesn't, shifting between them to find some way in which each different UBI scheme mentioned doesn't solve all of society's problems. But UBI isn't designed to solve all problems, it's designed to alleviate extreme poverty and undue suffering and by that metric it works remarkably well. Of course, that's the one metric that The Guardian doesn't mention.
Of course it doesn't solve wealth inequality. Why would it? Their main argument against each UBI scheme is that it "isn't sustainable" as if that somehow means it doesn't reduce poverty. Alaska's petroleum dividend is dubbed "unsustainable" because at some point in the future Alaska might run out of oil, and so the program is apparently a failure today? Finland's dividend is dubbed "unsustainable" because new political alliances can vote to overturn it, so that means it's a failure too? What kind of crappy metric is "sustainability" for a government spending program?
And then they criticize all of the various UBI schemes as "crowding out" other investments in poverty reduction, which is pretty rich coming from an economic school of thought that originated the very idea of UBI as a replacement for social service programs. Let's not forget it was the hardline conservatives of the 60s-80s who wanted to abolish government subsidies for affordable housing and food stamps and just give poor people cash money instead. They argued that government cheese was an infringement of personal liberties, and that poor people would spend cash payments the most efficient way possible by the magic of the free market, if only government would stop trying to tell them where and how to live. The whole idea of gutting our welfare state and replacing it with UBI is a republican wet dream, because it costs the government less, absolves government of responsibility for poor spending decisions by poor people exacerbating their poverty, and (perhaps most importantly) gives just as much money to billionaires as it does to homeless people and is thus seen as "more fair".
And then the cherry on top of this particular article is that their reporting is basically the opposite of the conclusions in the study they're citing.
The original study they're talking about is definitely written from a "progressive" liberal viewpoint, and it explicitly promotes the benefits of UBI for alleviating extreme poverty and then goes into some detail about why progressive prefer expanding the current social safety net instead (see previous paragraph). When The Guardian writes about this study to say "UBI doesn't work" it's kind of like Trump tweeting that the Mueller report "totally exonerates" him. Um, no. The exact opposite of that. You're lying in the most transparently obvious way about the content of the document you're referencing, in an attempt to sow confusion and spin public reaction among people who can't be bothered to actually read the thing for themselves to see what a baldface liar you are.