I am having a hard time finding an answer to this question for 18.04 LTS.
I used the following to find a list of options to configure.
gsettings list-keys org.gnome.desktop.peripherals.touchpad
It returned the following list:
touchpad
send-events
natural-scroll
tap-to-click
two-finger-scrolling-enabled
left-handed
click-method
speed
scroll-method
tap-and-drag
edge-scrolling-enabled
disable-while-typing
Out of this list, which of these options can be configured to be "false" to disable horizontal scrolling? Samuel Cavazos' answer seems close to what needs to be done, but the horizontal option does not appear to be available in the current list above. His answer, which is not applicable in 18.04, is as follows:
gsettings set org.gnome.settings-daemon.peripherals.touchpad horiz-scroll-enabled "true"
Was this option renamed to scroll-method? If so, what should the terminal line be to disable horizontal scrolling?
Best Answer
I found the answer to my own question, and so wanted to share what worked for me in case others are stuck. Pilot6's answer to the same question asked for 16.04 works with a little modification for 18.04. The following steps solve the issue:
sudo apt update
sudo apt install libinput-tools
sudo gedit /usr/share/X11/xorg.conf.d/40-libinput.conf
Option "HorizontalScrolling" "False"