If anything it should encourage private enterprise because you don't risk having zero money to eat and make rent
I think this is one of the critical pieces that everyone seems to ignore. It seems that most everyone thinks that UBI means more welfare and nothing changes culturally. I'd be shocked if that was the case.
I'm a decent writer, pretty solid cook, and I make pretty good beer. All of those things I do as hobbies because the risk in trying to do them as a job is too high for me. If I was given 2/3 or 3/4 of what I make now as UBI, I'd have to have a long talk with my wife about potentially quitting my job, being stay-at-home dad, and pursuing those hobbies as business ventures.
I can hardly imagine the boom in arts and culture that we'd see with UBI. All the starving musicians and artists who give up the dream to pay the mortgage would no longer have to. The sidewalk musician brightening our day would head home to a comfortable house, richer from the donations, but not starving if they are low for a day. I could see gardens and civic beautification projects exploding, as people with free time could invest it in their community. Kids would no longer be shipped off to day care with strangers. Parents could be more deeply involved in schools. Everyone with a crazy idea could pursue it, unlike now where most don't, because they can't afford to fail.
The parental engagement with kids may be the most significant impact financially. Kids who grow up in stable homes with involved parents do better in life than those who don't. They stay in school longer, stay out of trouble more, and, in general, become more productive members of society. If we can prevent 25% of the kids who get tangled up in the legal system and ER from doing that, either as kids or adults, that's a big savings for communities. If we can prevent 25% of the violent crime from happening, that's huge. And it could be more than that - most of the crime in my area is gang-driven, and the gangs form because the kids in them are desperate for a better life. If you can get paid enough to have a decent place to live, smoke weed, play video games, and shoot some hoops, being part of a gang is going to be a hard sell. And while the aforementioned weed smoker isn't going to be a productive member of society, if the choice is that or a gang-banger, I'll take the weed-smoker any day. The alternative is a serious negative impact on society, both in terms of happiness and overall financial well-being.
UBI will drive cultural change, the likes we haven't seen since abandoning agrarian society and moving into the mechanized one. I really think that with less poverty we'll see less chronic health issues (which increase hospital/ER costs tremendously) less crime (police and incarceration budgets are huge) more entrepreneurs (less organized labor and more individual and unique efforts, but potentially a broader tax-base) and there will be more people with expendable income to invest in those entrepreneurs.