Ubuntu – I upgraded from 17.04 to 17.10 on a Lenovo T540p which has broken two finger touchpad scrolling and right clicking

As per https://help.ubuntu.com/community/SynapticsTouchpad

You can determine your input devices (not just touchpad), by using the command xinput

From Terminal Using xinput

1. First you want to see what number your device is labelled as. Use the command xinput list to see all of your devices. (You could probably shorten this to a command like xinput list |grep Synaptic -n2, or something similar)

2. Note the id next to the Device.

3. Determine your current settings by doing the command xinput --watch-props YOURDEVICEID (YOURDEVICEID being the device id you noted in previous step)
4. You may wish to adjust sensitivity which is Synaptics Finger, but it is dependent on your actual touchpad. So you may have to tweak other ones as well. (Press Ctrl+C to exit).
5. Once you determine what you want to change you will input it with the xinput with the --set-prop switch.

Same Example as from top source below

xinput --set-prop YOURDEVICEID "Synaptics Finger" 50 80 257

This will adjust the sensitivity of the pad in general.

From Terminal using synclient

You can also find a configuration with synclient

1. Input the command synclient -l to view your current configuration. (You can also redirect this into an editable document if you want to manipulate it further with a command such as synclient -l > touchpadconfig)
2. You can set the value by doing a command like synclient LeftEdge=130 to set left edge of the touchpad to a coordinate 130.

Unfortunately there are lot of settings which can be adjusted, and you may need to adjust them yourself. However the man synaptics explains each of the parameters which can be set in fairly human readable terms.

Further Reading from Debian wiki

Further Reading from Arch wiki

You likely need to re-implement your synaptics touchpad configuration for libinput. The Arch wiki has a great page on Libinput that explains how configure libinput, both as runtime for testing, and also for persistent configuration.