Your argument is oversimplified. Landlords may be able to extract more money from people who net benefit from UBI, yes, but they will be able to extract less money from those who take a net loss from the policy. (I’m skeptical that landlords will actually be able to extract more because I believe most low income people who can afford rent now are likely unable to afford the means of subsistence in total, but this aside doesn’t affect the argument I’m making here.)

So the inflationary effect will probably be limited to low-income housing, which is already heavily subsidized by taxpayer dollars in the US, arguably even more inefficiently than the situation under a hypothetical UBI. It will probably be coupled with a deflationary effect at middle-to-upper income housing, depending on the nature of the benefit and the structure of the taxes used to fund UBI. If the policy is structured competently, there’s no reason that it is necessarily inflationary as a whole.