Mainland has not changed since the update. It never had covenants and still doesn't now. Some of the estate listings are confusing and seem like they are Mainland. But true Mainland will never have a covenant.
The problem is that LL has not given us a way to sort between estates with covenants and Mainland without them. They are both in the same land sales search and it's up to us to tp to each parcel and check and see if there is a covenant or not. Many of us have asked for there to be a way to sort, but none has been created as of yet.
To help people sort, I always list my land with "No Covenant" in the header. Another quick way for you to sort is to check the price per meter. If it is 14 or below, there's a 99% chance it's got a covenant and is estate land not Mainland.