The thing that always concerns me about UBI is that the government controls your salary. This is sort of true already on that they have the power to raise our lower taxes, but lowering UBI would affect far more people
UBI is not salary, and doesn't prevent you (or punish you) from earning a salary alongside it.
That said, I'd prefer a universal income to be fundamentally (e.g., Constitutionally) tied to a dedicated funding stream, equally divided, and not subject to regular legislative control.
I see it going in much the same way current governments in stable countries don't suddenly show up at your door saying you owe them 95% in tax. Refusing or delaying to pay your UBI would amount to that, an illegal tax.