My old laptop (Samsung np300v3a, running fresh Ubuntu 18.04) has a broken left trackpad button, that is always pressed. I have been trying to disable the physical keys, but keep the tap to click in order to retain this use of the trackpad.
I've tried modifying xinput button-map, set-props, and some synclient options. I can disable the left click with xinput, but this also disables the tap to click function.
Threads I've read:
Disabling One-Finger Tap-to-Click But Keep Two-Finger tap Ubuntu 12.04
How to disable physical mouse buttons below touchpad
If you upgrade to at least Ubuntu 18.10 or 19.04, there is a simple way :
create the file (and the directory) :
/etc/libinput/local-overrides.quirks
put in it this :
It work fine on my sony vaio pro 13. You may have to tweak the Match* lines, have a look at : https://wayland.freedesktop.org/libinput/doc/1.13.0/device-configuration-via-udev.html
good luck