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 work,
please add the output of libinput-list-devices to your question.
You also may want to have a look
at the Touchpad Indicator GNOME Shell extension.
