Question: Trackpad two finger scrolling and right-click issue with Ubuntu 17.10 (i386, 64bit, GNOME 3.26.1) on a Lenovo T540p (the model with a Intel Core i5-4210M Haswell CPU etc)

Answer: 
Update for other ThinkPad users, as per the hard work done [here](https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1722478), the workaround is as follows...

Edit the file `/etc/default/grub` and change the line:

```
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

```

to

```
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash psmouse.synaptics_intertouch=0"

```

then

```
sudo update-grub

```

and reboot.
As mentioned in the [answer by @hpotter40](https://askubuntu.com/a/971735), this is behavior is bug [LP #1722478](https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1722478). It affects a wide variety of relatively recent ThinkPad computers, and is still present in Ubtuntu 19.04. Three workarounds are discussed in the Launchpad issue. One is mentioned by @hpotter40 in his answer, the other two are here:

Option 1: Switch off Intertouch
-------------------------------

This is my favourite, as it is the simplest to configure.

1. Edit file `/etc/default/grub` and change the line

```
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

```

into this:

```
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash psmouse.synaptics_intertouch=0"

```
2. Execute:

```
sudo update-grub

```
3. Reboot.

Source: from [here](https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1722478/comments/45) and [here](https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1722478/comments/46). Also I just saw it's covered already in [another answer here](https://askubuntu.com/a/981648).

Option 2: i2c-801 module
------------------------

1. If your `/etc/modprobe.d/blacklist.conf` contains a line `blacklist i2c_i801`, remove it or make it into a comment.
2. Use [this technique](https://askubuntu.com/a/1030154) to reload the `i2c-i801` module after each resume from suspended state. You can of course also do that manually, in which case the commands are:

```
sudo modprobe -r i2c-i801
sudo modprobe i2c-i801

```

There is no need to `modprobe` this module at system start explicitly, as two-finger scrolling and two-finger-tap for right-clicking only breaks at the first resume from suspended state.

Source: from [here](https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1722478/comments/66).