I just finished installing Ubuntu 18.04 on a Asus UX391UA Zenbook and have run into trouble configuring the touchpad. The touchpad is recognized but Xorg is unable to configure it at startup.

The touchpad works okay in Wayland, although I am not an expert so am unable to translate its function to Xorg.

I am posting what I think is the relevant output to troubleshoot this issue. Please let me know if any more impormation is needed. Or point me to the relevant documentation so that I can troubleshoot the situation myself.

Many thanks in anticipation.

Relevant output of libinput-list-devices:

Device:           GDX1301:00 27C6:01F0 Touchpad

Kernel:           /dev/input/event10

Group:            8

Seat:             seat0, default

Size:             105x61mm

Capabilities:     pointer gesture

Tap-to-click:     disabled

Tap-and-drag:     enabled

Tap drag lock:    disabled

Left-handed:      disabled

Nat.scrolling:    disabled

Middle emulation: disabled

Calibration:      n/a

Scroll methods:   *two-finger edge 

Click methods:    *button-areas clickfinger 

Disable-w-typing: enabled

Accel profiles:   none

Rotation:         n/a

Excerpt from Xorg.0.log:

[    75.047] (II) config/udev: Adding input device GDX1301:00 27C6:01F0 Touchpad (/dev/input/event10)

[    75.047] (**) GDX1301:00 27C6:01F0 Touchpad: Applying InputClass "libinput touchpad catchall"

[    75.047] (II) Using input driver 'libinput' for 'GDX1301:00 27C6:01F0 Touchpad'

[    75.047] (**) GDX1301:00 27C6:01F0 Touchpad: always reports core events

[    75.047] (**) Option "Device" "/dev/input/event10"

[    75.047] (**) Option "_source" "server/udev"

[    75.153] (II) event10 - GDX1301:00 27C6:01F0 Touchpad: is tagged by udev as: Touchpad

[    75.153] (II) event10 - GDX1301:00 27C6:01F0 Touchpad: device is a touchpad

[    75.153] (II) event10 - GDX1301:00 27C6:01F0 Touchpad: device removed

[    75.184] (**) Option "config_info" "udev:/sys/devices/pci0000:00/0000:00:15.1/i2c_designware.1/i2c-7/i2c-GDX1301:00/0018:27C6:01F0.0002/input/input19/event10"

[    75.184] (II) XINPUT: Adding extended input device "GDX1301:00 27C6:01F0 Touchpad" (type: TOUCHPAD, id 13)

[    75.184] (**) Option "AccelerationScheme" "none"

[    75.184] (**) GDX1301:00 27C6:01F0 Touchpad: (accel) selected scheme none/0

[    75.184] (**) GDX1301:00 27C6:01F0 Touchpad: (accel) acceleration factor: 2.000

[    75.184] (**) GDX1301:00 27C6:01F0 Touchpad: (accel) acceleration threshold: 4

[    75.186] (II) event10 - GDX1301:00 27C6:01F0 Touchpad: is tagged by udev as: Touchpad

[    75.186] (II) event10 - GDX1301:00 27C6:01F0 Touchpad: device is a touchpad

[    75.187] (II) config/udev: Adding input device GDX1301:00 27C6:01F0 Touchpad (/dev/input/mouse2)

[    75.187] (II) No input driver specified, ignoring this device.

[    75.187] (II) This device may have been added with another device file.

I had the same issue with Debian.
Based on https://wiki.debian.org/fr/SynapticsTouchpad, I corrected it by creating /etc/X11/xorg.conf.d/50-touchpad.conf with the following content :

Section "InputClass"

    Identifier      "Touchpad"                      # required

    MatchIsTouchpad "yes"                           # required

    Driver          "libinput"                     # required

    Option          "MinSpeed"              "0.5"

    Option          "MaxSpeed"              "1.0"

    Option          "AccelFactor"           "0.075"

    Option          "TapButton1"            "1"

    Option          "TapButton2"            "2"     # multitouch

    Option          "TapButton3"            "3"     # multitouch

    Option          "VertTwoFingerScroll"   "1"     # multitouch

    Option          "HorizTwoFingerScroll"  "1"     # multitouch

EndSection

Then I added my account to the input group.

Cheers !