Apple released Safari 16.4 for macOS a couple of weeks ago. You may have noticed that Safari 16.4 has support for smooth key-driven scrolling on macOS. Smooth scrolling means that when you press the arrow keys to scroll down or up on a web page, the scrolling is animated rather than immediate. I personally don't mind smooth scrolling, but I've heard from other people who don't like it. Unfortunately, there's no way to change the scrolling behavior in the Safari Preferences window. Err, Settings window. As the developer of the Safari extension StopTheMadness, I often have a solution to your Safari problems, and this case is no exception. However, the solution is not in StopTheMadness but rather in the hidden Debug menu of Safari.
If you haven't already enabled the Debug menu in Safari, you first need to give Full Disk Access to Terminal in System Preferences. Err, System Settings.
My blog post macOS Containers and defaults explained why Terminal needs Full Disk Access. Next, you need to quit Safari and enter the following command in Terminal:
defaults write com.apple.Safari IncludeInternalDebugMenu -bool true
Then launch Safari, open the Debug menu at the end of the main menu, select WebKit Internal Features, and uncheck "EventHandler driven smooth keyboard scrolling".
Now you can once again enjoy your lack of smoothness!