RSA is not UBI, UBI literally means Universal Basic Income, it's not for no income/low income people, it's universal.
You are conflating the concept of UBI with social welfare, they are different things and it's a bit annoying to see the erosion of the UBI concept into social welfare, I've noticed an uptick of this the past year or so, no idea where it's originating from...
Agreed I butchered it, but what is the concrete difference right now for someone that has no job (so where UBI is relevant) with social welfare and "UBI" if in the end, that person gets a monthly income that is somehow guaranteed?