On landlord I can’t think of a proper synonym. Property owner and proprietor are broader categories of what a landlord is. They don’t mean the person you’re paying rent to for your housing.
To play along with this game, one can say that replacing "landlord" with "property owner" is offensive to those with ancestors who were deemed property.
It ought to be offensive to women because it suggests they can't be landlords-- a word which is already perfectly gender neutral in American English as far as I can tell.
