I bought it in 2019 before it was a rental.
I forgot about that, as I didn't refresh my memory on this by re-reading this whole thread. Safe harbor is not an option then, unfortunately.
But why bother listing it separately? Include what you paid for it, in the cost basis of the entire property. Any and all assets purchased before the property was converted to a rental, have the same exact in service date. So just include it in the cost basis of the property and be done with it. Makes life a whole lot easier and simpler in the future when you sell or otherwise dispose of the property.
