"fn" keys and combinations are implemented by your actual BIOS, and are not controlled by the operating system.
At least for disabling the touchpad, you can do that using a script or just disable tap-to-click.
For example, this is the script I use to disable tap-to-click with a shortcut key:
#!/bin/bash
STATUS=$(gsettings get org.gnome.desktop.peripherals.touchpad tap-to-click)
case $STATUS in
true )
gsettings set org.gnome.desktop.peripherals.touchpad tap-to-click false
gsettings set org.gnome.desktop.peripherals.touchpad click-method 'areas'
# 2021-07-05 Change also click method: area when tap is off
# notify-send "Tap-to-click Off"
;;
false )
gsettings set org.gnome.desktop.peripherals.touchpad tap-to-click true
gsettings set org.gnome.desktop.peripherals.touchpad click-method 'fingers'
# notify-send "Tap-to-click On"
;;
esac
- Save the contents in a text file, e.g.
~/bin/toggletouchpad.
- Make that file executable: right-click, select the properties tab to set the executable bit.
- Create a shortcut key to toggle the setting, and as command, enter the full path name of the script:
/home/<yourlogin>/bin/toggletouchpad (where <yourlogin> stands for your login name).
Remove the comment sign # if you like to see a notification when you change the status.
