Prices would go up for everyone, making the value prop worse for everyone.

Rents are high in SF because there is extremely high demand for those apartments at high prices, because they allow access to high incomes. The value of living in SF for a random serivce worker is not increased by them getting a $2k UBI cheque, it is decreased. For the tech workers driving the demand, $2k a month is not going to do much to change the value they assign to housing in SF either way. So I do not see how the UBI cheques would increase demand, and therefore rent, for housing in SF.