GS724Tv6 How to disable UPnP?

Bought GS724Tv6 switches, which are now spamming my network with SSDP NOTIFY packets.

From what I gathered this is due to some UPnP advertising.

How can I stop these switches from doing that?

In the manual (GS724Tv6_GS748Tv6_UM_EN.pdf) I read:

"Manage UPnP switch discovery
By default, Universal Plug and Play (UPnP) is enabled on the switch."

and I could disable it under

"Select System > Management > Switch Discovery.
The Switch Discovery page displays."

Sadly there is no such option, not does the Site Index list 'Switch Discovery' anywhere.

=> How can I disable UPnP?