"Scroll Reverser is a free Mac app that reverses the direction of scrolling. It is available for macOS 10.4 through 10.13.
It has independent settings for trackpads, mice and Wacom tablets, and for horizontal and vertical scrolling. "
That said, I do consider it a ding against MacOs, because it's ridiculous that I'm forced to use third-party tools for such basic functionality. (Other examples: USB-tethering with non-Apple phones requires hunting down and installing third-party drivers. A feature that just works, out-of-the-box, on every other system I've ever used.)