It is disabled if the nvidia driver is detected. See here.
X11 doesn’t really have any facilities to forward touchpad gestures to applications. I think the best you can do at the moment is simulating Control++ or - key presses.
You can configure that for fusuma:
pinch:
in:
command: 'xdotool keydown ctrl click 4 keyup ctrl'
out:
command: 'xdotool keydown ctrl click 5 keyup ctrl'
Have you looked at the X11 gestures GNOME shell extension (it’s in the AUR)? Maybe you’ll find it better than fusuma.