What any group think isn't monolithic of course.
Regarding dubsartur's point: generally, I don't think this is hugely a point of debate about UBI in the UK: there aren't actually that many varied systems for cash payment for living costs since everything got rolled into the awful Universal Credit system, which everyone except the Conservatives now kind of dislikes (arguably UC isn't actually that bad as a theoretical delivery system for benefits, it's just that it was cut back really hard while being implemented so people lost money hard as they moved onto it and it had huge IT problems so it's got an unsalvageable reputation on the left). I think the two big things which would be necessary but tricky to realise the full potential of a basic income would be to have it used for student living cost support and to dovetail it properly with pensions - there'd be some pushback on the latter I suspect. The other thing to note re the mix of subsidies is that you probably actually do still have to manage separate housing and disability payments even with a UBI: housing costs are so variable in the UK that paying just enough to someone in London would mean dumping vast additional sums on people who live in poor bits of the north, and disability likewise has hugely variable costs that probably need independent assessment. The big financial benefits to UBI aren't actually the decreased administration costs, but the income security, which gives you a far more flexible labour force (easier to move and retrain if you're not too poor to do so when out of a job), and to things like healthcare where lower stress levels can genuinely decrease strain on the system.
The big anti-UBI argument in the UK is "if you pay people without forcing them to work they won't work". Which actually we know from pilots isn't true, but it's still the core argument one hears. I don't know a lot about the demographics of UBI support: most of the places that seem to have strong UBI campaigns are urban and northern. The Lib Dem group in Hull is where a lot of the most pro-UBI people in the party hang out, Sheffield has a strong UBI network, and Leeds council recently passed a pro-UBI motion put forward by the Liberal Democrat group there. So there's definitely an explicit pro-UBI activist network in the UK in a way that there wasn't five years ago. My guess is that UBI support tends to skew more northern, urban, educated, and young, in general: it tends to appeal most easily to people whose work is irregular in its hours and availability, so contract and gig workers, who again tend to be younger and more urban.
As to the Lib Dems' stances on poverty: we're against it, unsurprisingly, but there's a difficult internal split because of the party's time in government (2010-15) between members who argue that the austerity measures taken during that period were justified to stabilise finances and people like me who think they weren't justified and leaned far too hard on the poorest to pay for problems they hadn't caused. In general the party agrees more about the future than the past on this, and has sat left of Labour on benefits for the poorest since about 2016. (Labour have generally tended to advocate spending more money in total in recent years, but much of that is on universalising benefits that are currently means tested - for example, making free childcare available to middle class as well as badly off citizens). Part of the issue for both Labour and the Lib Dems is that both are very, very middle class parties with lots of people talking about social issues who've never really experienced them, and who are nominally committeed to "making politics more diverse" but don't understand what the barriers to that look like when you're on the other side of them. I mean I include myself in that, but I do what I can to work with people who do understand these things on a more personal level. The Conservatives meanwhile now have older white working class people among their core voters, mostly appealing to them on more conservative cultural principles.
Re what Baragon said about the UK being four different countries: yes, though some are more different than others.
Sorry that was a bit of a ramble, hopefully it contained some interesting oddments.
