macOS Sonoma now has an option to disable Pointer Acceleration built in to the System Settings:
https://apple.stackexchange.com/a/461057/36202
This app disables mouse acceleration on macOS.
You've probably already heard of this command:
defaults write .GlobalPreferences com.apple.mouse.scaling -1
Unfortunately, it also has the side effect of making your mouse movement insanely slow. Unlike that command, this app disables acceleration with no side effects.
Also want to get rid of scroll acceleration? This app works well when paired with Discrete Scroll.
Download the release, drag it into /Applications, then go to Settings -> Users & Groups -> Login Items and add NoMouseAccel.app to the list.
This is basically just a cleaned up and packaged version of the code from https://forums3.armagetronad.net/viewtopic.php?t=3364. All credits to the author.
As it turns out, this works due to a... bug? feature? in
IOHIDFamily/IOHIDEventSystemPlugIns/IOHIDPointerScrollFilter.cpp.
The acceleration is reset, then the new acceleration is checked for a negative value.
If it is negative, the function immediately returns without configuring a new acceleration
value, which gives us the "unaccelerated" behavior.
You may notice that this file also handles scroll acceleration. Why doesn't this work for scroll, you ask? The answer is that for scroll acceleration, the acceleration is checked before the value is reset, and so setting the scroll acceleration to a negative value has no effect.