If we introduce UBI it would probably be one of the first times in history that society addresses major changes without war, revolution or other upheaval. My prediction is that inequality will grow, a lot of people will lose their jobs, but nothing will change fundamentally without a major conflict.
We see that already with climate change. There clearly is no will to really address the issues. We'll have sea levels rising, millions of refugees and somehow deal with that. We will not prevent that.
A large part of climate change denial is driven by economic forces. The oil and transportation industries have built an economy that relies on fossil fuels. As soon as alternatives are cheaper, there will be a transition. We are seeing that in the energy sector now where solar has gotten cheaper than coal. Power companies are starting to make the transition to wind and solar. IMO, the best thing we can do to solve the climate crisis is to make the economics of non-fossil fuel energy sources impossible to compete with OR close the loop on CO and CO2 emissions (converting atmospheric carbon back into fuel).
https://en.wikipedia.org/wiki/Tragedy_of_the_commons
Unfortunately, capitalism is one of the primary drivers of this. But it's also correlated to any authoritarian system, as well as deregulated systems that use Social Darwinism.
The heart of the problem is an inability for people to organize and address societal problems in a non-reactionary way by means of central planning. Which means that the solution is inherently leftist politically. We can pretend that there are rightist solutions (the invisible hand of the free market, unfettered capitalism, etc) but there is ample evidence that those don't work in practice and are even accelerating global climate change and the collapse of ecosystems.
War is always about money. If we flatten wealth inequality via UBI, that suggests that the impetus for war may be diminished. So expect backlash from those in power or whose wealth is derived from armed conflict.