Squeak is a macOS app that changes the scroll direction to natural when scrolling with a trackpad and normal when scrolling with a mouse. It does this automatically based on the device being used when scrolling. It lives quietly in the menu bar and can be set to launch on each login.
No. Squeak is not a sandboxed app so it cannot be submitted to the App Store.
MIT
Thanks to Sindre Sorhus for LaunchAtLogin and to the author of this article at ShadowFacts.