Apple - How to separate "mouse" and "trackpad" settings?

I had the same problem when I started to use macOS.

I installed this little utility, which lets you reverse the scrolling behavior only for the mouse:

Scroll Reverser for macOS

Update 2020/12/03: As other's have pointed out, this is not a feature of Karabiner in newer versions.

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It appears that this is integrated in the Karabiner app so it works out of the box without any custom XML (which are described above).

You'll need the following settings:

• Karabiner Preferences > Change Key > Karabiner core settings > Exclude devices > Don't remap Apple's pointing devices
• Karabiner Preferences > Change Key > Pointing Device > Reverse scrolling direction > Reverse Vertical Scrolling

Set the Enable Natural Scrolling setting in the Mouse/TrackPad PrefPane to 'enabled'. This allows for the internal trackpad to work as it's supposed to. Any connected non-Apple external mouse will scroll in their own natural way.

I found myself in the exact same boat (preferring Natural for TrackPad and normal for Mouse), and in case anyone attempts to do the same, I did file a bug report against Apple for this. They closed it rather briefly with the words "This is intentional" and no other explanation.

I'm guessing that it's a common request, and they're just tired of hearing it.