UBI isn't only great in theory, a number of countries are only a finger's breadth away from having implemented it. I live in Germany.
There's no way for me to not be under health insurance (working without is actually illegal and the state pays it for unemployed people).
If i lose my job the state keeps paying me 70% of my original wage for an amount of time proportional to how long i worked, and after that drops me to a base level i can live on (though possibly i would need to move). The only things i need to do to keep receiving it is to prove i keep applying for jobs by sending them application copies twice a month, and to not reject reasonable job offers the work bureau sends my way. (And yes, people have rejected such and sued and won in court, with no extra cost to them.)
And even beyond that, there's a minimum wage, and even a state income offset program to allow people with extraordinary expenses (caring for sick relatives, etc.) to receive money if their income minus said expenses falls under a certain limit, equivalent to people on long term unemployment aid.
It's implemented in various different programs, and not in one neat bundle, but in terms of real-politik UBI is already here.
Sure, people can still live in poverty even here, but this is not due to a lack of aid, but due to people's own decisions. (Continuing to live in expensive areas, refusing to get aid, etc.)