If it's universal and meaningful (that is: everybody will have that much more money to spend), you can't finance it unless you massively increase taxes (at which point people won't actually be able to spend it, because they'll need it to counteract the increased taxes). You can fund it only by not actually giving it to everybody in terms of real buying power. You might still pay it out but for the median worker their taxes will be raised, so it's only a nominal thing, they can't buy any more stuff.
Essentially then, you have the same idea you have today: those who will rely on UBI are the same people who rely on social benefits today, and those who do not get it are the ones who will have to fund it (with a slightly enlarged soft border between the two). The stigma isn't because people know that you get social benefits (the records aren't public), it's that they don't see you working.
The cut-offs are an issue, but we already have Mini (up to 450€) and Midi Jobs (up to 1300€) where you'll not get any reduction in benefits for 100€ and 20% of whatever you make on top will also not affect your benefits. That's not a perfectly soft threshold, but it's not a hard cut-off either. The thresholds that you lose money at are much higher (e.g. earning just a little bit too much to be eligible for subsidized housing, which is close to the median salary in most states).
Essentially then, you have the same idea you have today: those who will rely on UBI are the same people who rely on social benefits today, and those who do not get it are the ones who will have to fund it (with a slightly enlarged soft border between the two). The stigma isn't because people know that you get social benefits (the records aren't public), it's that they don't see you working.
The cut-offs are an issue, but we already have Mini (up to 450€) and Midi Jobs (up to 1300€) where you'll not get any reduction in benefits for 100€ and 20% of whatever you make on top will also not affect your benefits. That's not a perfectly soft threshold, but it's not a hard cut-off either. The thresholds that you lose money at are much higher (e.g. earning just a little bit too much to be eligible for subsidized housing, which is close to the median salary in most states).