First of all, try if this dconf setting is of any use:
gsettings set org.gnome.desktop.peripherals.touchpad disable-while-typing 'false'
It was stated with false while the name would imply true.
This setting should be for Xserver configurations:
gsettings set org.gnome.desktop.peripherals.touchpad send-events 'disabled'
Notebook also may disable the touchpad with Fn + F5, you may try that.
If that doesn't word, please add the output of libinput-list-devices to your question. You also may wanna have a look at this:
