Ubuntu – How to configure touchpad two fingers tap as middle click in ubuntu 19.10? Libinput is used

First off does the touch-pad support two finger scrolling? If so the result of synclient -l would be nice to edit

add the output of the command synclient -l.

Parameter settings:
    LeftEdge                = 1775
    RightEdge               = 5503
    TopEdge                 = 1652
    BottomEdge              = 4662
    FingerLow               = 24
    FingerHigh              = 29
    FingerPress             = 255
    MaxTapTime              = 180
    MaxTapMove              = 245
    MaxDoubleTapTime        = 180
    SingleTapTimeout        = 180
    ClickTime               = 100
    FastTaps                = 0
    EmulateMidButtonTime    = 75
    EmulateTwoFingerMinZ    = 10
    EmulateTwoFingerMinW    = 6
    VertScrollDelta         = 111
    HorizScrollDelta        = 111
    VertEdgeScroll          = 0
    HorizEdgeScroll         = 0
    CornerCoasting          = 0
    VertTwoFingerScroll     = 1
    HorizTwoFingerScroll    = 0
    MinSpeed                = 1
    MaxSpeed                = 1.75
    AccelFactor             = 0.0359131
    TrackstickSpeed         = 40
    EdgeMotionMinZ          = 29
    EdgeMotionMaxZ          = 159
    EdgeMotionMinSpeed      = 1
    EdgeMotionMaxSpeed      = 445
    EdgeMotionUseAlways     = 0
    TouchpadOff             = 0
    LockedDrags             = 0
    LockedDragTimeout       = 5000
    RTCornerButton          = 2
    RBCornerButton          = 3
    LTCornerButton          = 0
    LBCornerButton          = 0
    TapButton1              = 1
    TapButton2              = 3
    TapButton3              = 2
    ClickFinger1            = 1
    ClickFinger2            = 1
    ClickFinger3            = 1
    CircularScrolling       = 0
    CircScrollDelta         = 0.1
    CircScrollTrigger       = 0
    CircularPad             = 0
    PalmDetect              = 0
    PalmMinWidth            = 9
    PalmMinZ                = 199
    CoastingSpeed           = 20
    CoastingFriction        = 50
    PressureMotionMinZ      = 29
    PressureMotionMaxZ      = 159
    PressureMotionMinFactor = 1
    PressureMotionMaxFactor = 1
    ResolutionDetect        = 1
    GrabEventDevice         = 1
    TapAndDragGesture       = 1
    AreaLeftEdge            = 0
    AreaRightEdge           = 0
    AreaTopEdge             = 0
    AreaBottomEdge          = 0

You can change the setting of the synclient by adding to the startup application a new application with the following command:

xterm -e synclient "EmulateTwoFingerMinZ=10"

This would change the setting of EmulateTwoFingerMinZ to the value of 10

Found similar answer here: How to get two-finger scolling to work?

Well, this is not the direct answer, but a suggestion and examples. If you run xinput, you will get list of your devices. Then run xinput list-props $id where $id is your touchpad id in the list.

You will have a list of options like this:

$ xinput list-props 13
Device 'SynPS/2 Synaptics TouchPad':
    Device Enabled (135):   1
    Coordinate Transformation Matrix (137): 1.000000, 0.000000, 0.000000, 0.000000, 1.000000, 0.000000, 0.000000, 0.000000, 1.000000
    Device Accel Profile (268): 1
    Device Accel Constant Deceleration (269):   2.500000
    Device Accel Adaptive Deceleration (270):   1.000000
    Device Accel Velocity Scaling (271):    12.500000
    Synaptics Edges (292):  1765, 5371, 1637, 4453
    Synaptics Finger (293): 25, 30, 0
    Synaptics Tap Time (294):   180
    Synaptics Tap Move (295):   234
    Synaptics Tap Durations (296):  180, 180, 100
    Synaptics ClickPad (297):   1
    [...]

You can change all of these on-the-fly with xinput set-prop $id $propId $value where $id is the device id, $propId is property id in brackets and $value is what you want it to be. For example:

xinput set-prop 13 135 0 sets Device Enabled (135) to 0 and this will disable the touchpad.

You will need descriptions of properties and a way to make your changes permanent. Descriptions can be found in man synaptics, but wait, they are in another cryptic format! Let's see why.

To make changes permanent, you need to create conf file in /etc/X11/xorg.conf.d, for example 30-tochpad.conf with contents like these:

    Section "InputClass"  # you can read more in `man xorg`
            Identifier "all touchpads"  # just a name for this config
            MatchIsTouchpad "on"  # enables this config for all detected touchpads
            Driver "synaptics"  # enables synaptics-specific options below

            # This will disable the device
            #Option "Ignore" "1"

            # There are options that are generic for input-devices or mouse-like devices, see `man evdev`:
            Option "ButtonMapping" "0 0 0 0 0 0 0"  # i disabled all buttons here, for example

            # Here go options from `man synaptics`
            Option "VertTwoFingerScroll" "1"
            Option "HorizTwoFingerScroll" "1"
            Option "PalmDetect" "1"
            Option "ClickPad" "0"                
            # ...etc...
    EndSection

So, man synaptics describes options for xorg.conf and tells how they correspond to xinput list-props output.

PS. I tried to configure trackpoint on my ThinkPad X220 to have only two-fingers-scroll enabled, without clicks or mouse movement. I failed. Maybe you will manage to do what you want (there was an option to disable everything but clicks, maybe Synaptics Off).

Sources, more examples and unicorns:

https://wiki.ubuntu.com/X/Config/Input

https://wiki.archlinux.org/index.php/Touchpad_Synaptics