Linux usability hack (XFCE in this case):

You have a touchpad and want to reverse scroll direction on ALL apps, including Qt, to match smartphone behavior:

find the touchpad device ID:
# xinput --list

Logitech Unifying Device. Wireless PID:4024 id=9 [slave pointer (2)]

Do this once when you login:

# xinput set-prop 9 "Evdev Scrolling Distance" -1 -1 -1