What if the value to someone is keeping people busy and thus not challenging the status quo? Or what if the job is useless to society but still makes some money?
Those are still very poorly-defined (what is "keeping people busy"? what is "useless to society"? Examples, maybe?), so it's hard to say anything about them. That said, I don't see why reducing the labor supply would eliminate jobs like those before other jobs.
I'm just kinda reflecting what I read about a book called "bullshit jobs", where he gives examples like telemarketing and a lot of paper pushing admin positions. Basically anything that society as a whole wouldn't notice disappearing. I've heard criticisms like there's less bullshit jobs than he says there is, but still.
Well, telemarketing isn't useless. It is irritating, but it does provide real value to many companies in the form of customer acquisition (also, it takes a very small number of people to do a LOT of calls, so there probably aren't very many of these). "Paper pushing admin" isn't necessarily useless either - some things are just human-intensive to document or coordinate.
In either case, I don't see anything special about these jobs that would make them the first to disappear in the face of UBI.