How to Configure Touchpad Buttons?

$ xev -event button | grep button
xev: warning: could not set default locale
    state 0x0, button 1, same_screen YES
    state 0x100, button 1, same_screen YES
    state 0x0, button 3, same_screen YES
    state 0x400, button 3, same_screen YES
    state 0x0, button 1, same_screen YES
    state 0x100, button 1, same_screen YES
    state 0x0, button 3, same_screen YES
    state 0x400, button 3, same_screen YES
    state 0x0, button 1, same_screen YES
    state 0x100, button 1, same_screen YES
    state 0x0, button 1, same_screen YES
    state 0x100, button 1, same_screen YES
    state 0x0, button 2, same_screen YES
    state 0x200, button 2, same_screen YES
    state 0x0, button 2, same_screen YES
    state 0x200, button 2, same_screen YES
    state 0x0, button 2, same_screen YES
    state 0x200, button 2, same_screen YES
    state 0x0, button 1, same_screen YES
    state 0x100, button 1, same_screen YES
    state 0x0, button 3, same_screen YES
    state 0x400, button 3, same_screen YES
    state 0x0, button 1, same_screen YES
    state 0x100, button 1, same_screen YES
    state 0x0, button 1, same_screen YES
    state 0x100, button 1, same_screen YES
    state 0x0, button 3, same_screen YES
    state 0x400, button 3, same_screen YES
    state 0x0, button 1, same_screen YES
    state 0x100, button 1, same_screen YES
    state 0x0, button 3, same_screen YES
    state 0x400, button 3, same_screen YES
    state 0x0, button 1, same_screen YES
    state 0x100, button 1, same_screen YES

From the results, on the touchpad (same for top and bottom two buttons):
Button 1 = left click
Button 3 = right click

On the mouse, the middle button = Button 2.

So, for the touchpad, I should change button 3 to Button 2?

But the command “xinput set-button-map "SynPS/2 Synaptics TouchPad"” did not seem to effect any change.

Perhaps the Xorg server is taking instructions from libinput instead of Synaptics driver? What do you reckon?