Since Ubuntu 21.04 my fix to reassign the middle trackpad click using xinput to "left click" no longer works. Now whenever my hand drifts to the middle of the trackpad, and I click on an application icon, I open up a copy of the current application. Or if I am in a program I end up pasting something I didn't want to. So I tried instead gnome-tweaks, which you can easily install using apt-get in terminal:
sudo apt-get install gnome-tweaks
Now lauch gnome-tweaks (e.g. by typing gnome-tweaks in Terminal) and select "Keyboard and Mouse". There is a section there called "Mouse click emulation". There are three settings:
- Fingers: all single trackpad clicks are left-clicks but you can simulate a right click by tapping with two fingers. I find this the most comfortable setting.
- Area: this is the default. the trackpad is divided into three areas. The bottom middle of the trackpad is middle click, leaving very little space for left-click which is dominant.
- Disabled: all clicks on the trackpad are left-clicks. I find this useless as you must have right click in many cases.
There is also a setting to disable middle click paste. I turned that off as I do not want middle click at all. Middle click makes sense with a mouse where you have tactile feedback as to what you are pressing but on a featureless trackpad you can only middle-click reliably if you stare at it the whole time. For terminal copy and paste I use shift-control-c and shift-control-v. With option 1 above you can still have middle click paste with a three-finger tap.