I hope you don't take this as a negative, but sometimes I wish I could think like people like you, very positive, but maybe I'm old/cynical?

There is a problem with "plus some so you can participate in society"

In a massive society this will never be agreed to. The 'some' here will never be enough. Too little and it's not UBI, too much and impossible to fund. Who is going to define what a luxury is? Is owning your own home a luxury, a car, washer and dryer?