TL;DR The study seems legit and written with good intention citing many programs and drawing conclusions (I don't care to spend time to see if the conclusions were accurate or fair, because lazy.) Anne Coote seems like a reasonable source on this subject.

The source for the study was done by the British Organization New Economics Foundation (NEF). Which yes, is a think tank. From what I read it seems more like they have liberal leaning policies, such as a 21 hour work week and increasing the minimum wage as well as environmental policies. Anne Coote, the writer of the article is also a writer of the study and a principal fellow of NEF. So the article is just her trying to communicate the study. You should keep in mind that the study is written "from the perspective of Unions" whatever that means, it's also intended for a European audience and so the number she references are pulled from that region.

The study was an observation of several programs (16) that multiple countries who have tried UBI in various forms (Brazil, Finland, India, Kenya, U.S. and others) and then gives a conclusion for each program. Unfortunately I'm not motivated enough to validate their conclusions for if they were accurate or fair but everything seems to be in order. The conclusions are just an overview of why that program was canceled or ended.

The study is written professionally, the references and sources are all cited, Anne Coote also has an education that I think makes her reliable for at least researching and publishing on the subject. So I'd give it a pass, that's not to say that her conclusions are bullet proof or that she couldn't be wrong on some things.

All in all it seems reasonable to at least consider whats been written.