Debian 9 zaměnil synaptic za libinput.

Konfigurační soubory zde

/usr/share/X11/xorg.conf.d
/etc/X11/xorg.conf.d

Moje nastavení touchpadu

/etc/X11/xorg.conf.d/30-touchpad.conf

Section "InputClass"
    Identifier "touchpad"
    Driver "libinput"
    MatchIsTouchpad "on"
    Option "Tapping" "on"
    Option "ScrollMethod" "edge"
    Option "DisableWhileTyping" "on"
    Option "TappingButtonMap" "lmr"
EndSection