I haven't read through all the responses so far. But my initial impression is that folks have you going around your elbow to get to your thumb.
Since the property was a 2nd home or personal residence in 2018 and was never ever ever a rental property in 2018, under no circumstances will you report this sale in the rental section. You have to report the sale in the "Sale of Business Property" section. It's under the Personal Income tab (business tab if using Home & Business desktop or Self-Employed online version) under the Less Common Income section.
