Nobody can agree how big UBI should be, and people talk past each other. Small UBI, like poverty level, could replace welfare but wouldn't be enough to survive on without doing something about housing and healthcare. Big UBI would be enough for good life, like median income, but not affordable with current economy and create inflation.

There is something in between that would be enough to survive, with small UBI, universal healthcare, and guaranteed housing.

You've got to start somewhere. Even a small UBI, like the one Alaska has, is better than nothing. Replacing welfare with a UBI at the same level would already be a massive improvement because you'd get rid of the poverty trap. From there you can grow it as much as the economy demands.