Mouse / Touchpad Buttons above touchpad not working

I have a rather new Lenovo P14s running Ubuntu-MATE 21.10.

How can I activate the left and right „mouse“ button on the touchpad (marked red). Currently they are completely inactive. (under Linux, not (dual boot) under Windows so not a hardware issue)

The green corners on the touchpad itself do work as mouse buttons, even hold and drag (i.e dragging around Windows on screen).

(under MATE there is no such thing as gnome-tweak, only a mate-tweak with nothing specific into this direction)

In my case these were disabled. I was able to enable them. Open your setting - mouse and touch-pad it should look something like this.

FYI: it is on ubuntu 20.04