Touchpad stopped working 20.04

This is solution, that has worked for me:

sudo rmmod psmouse
sudo modprobe psmouse proto=imps

or

sudo modprobe -r psmouse && sudo modprobe psmouse proto=imps

To make it permanent, edit:

sudo gedit /etc/modprobe.d/options

and add line:

options psmouse proto=imps

NOTE:

This fix will make the touchpad be recognized as a mouse instead, which might remove some features specific to touchpads such as disable while typing.

Hope this helps.

I've been using 20.04 since august and just and at the end of August 2020, suddenly the touchpad/trackpoint stopped working on my Lenovo Thinkpad X1 extreme.

After struggling, getting it partially working, and eventually trying to re-install 20.04 3 or 4 times to fix the issue (initial install was fine), I found that the problem may have been introduced in the kernel 5.4.0-47-generic.

To work around this, I select the older kernel 5.4.0-42-generic at boot time by accessing the GRUB menu and going to Advanced Options.

Now I'm able to use the trackpad/trackpoint as before.

I still have a bit of a display issue with suspend, but at least I can work on my laptop again.

To configure the kernels and defaults to set, this Ask Ubuntu question is a good resource.

UPDATE

I raised a bug with ubuntu, and managed to resolve the issue in my case by changing the Config->Graphics Device value from Discrete Graphics to Hybrid Graphics. With Hybrid Graphics set in BIOS and running the lastest kernal/updates as of 2020-11-6 I'm able to use my trackpad/trackpoint.

You can try reinstalling touchpad driver (synaptics in your case):

sudo apt purge xserver-xorg-input-synaptics
sudo apt autoremove
sudo apt update
sudo apt install xserver-xorg-input-synaptics

Restart and check.