Yes. I'm opposed.
Simply saying "everyone should get enough money from the government to live" has a lot of problems. The most obvious being that cost of living varies substantially from one place to another. And peoples needs vary substantially as well. So where do we set the number?
You'll also need to figure out how to combat the massive inflationary effects that would occur.
But imo, the biggest issue is what happens in the long term. Say a nation gives its citizens a UBI. Now wait 100 years. What happens? Well what happens is that, assuming this doesn't collapse the economy some other way, and assuming this is a democratic nation, everyone will start taking UBI for granted, and will start thinking "you know, if only I had a little more free money, I could afford that nice shirt I saw my neighbor wearing yesterday...". And because "free money for everyone" will be a popular political platform, the UBI amount will go up and up and up, with little thought put into how to continue funding it. The government accrues more and more debt over time funding the program, until finally the government can no longer continue paying its debtors, and the country collapses into chaos.
Instead, I'm in favor of a citizen's dividend, which is tied to the nation's economic output. A good example is how Alaskans get a dividend, since they agreed to allow private companies to extract the oil from their state. Land value taxes could work like this. Carbon taxes could work like this. If you want to make sure everyone is fed and housed, then that is a very noble goal - but it should be accomplished by providing people with food and housing. And I think it is right and fair that the people of a nation should be compensated for the use of their land and the negative externalities they endure - but how much they are paid out should not be coupled to the cost of living. It should be well known to be an independent, unpredictable, and highly variable amount that they can't rely on, so that they never gain the expectation that they will always have endless free money to spend however they please.