How to connect to Wi-Fi AP through WPS? All ways will be nice: configs, CLI, GUI - anything.
Connect through WPS on a windows setup, where it works out of the box.
Then open up the network settings on that setup, where it allows you to display the network password that was exchanged through WPS.
Copy that password to your ubuntu setup.
Next write a critical mail to the ubuntu community to express your frustration about the lack of such a basic UI feature given that its functionally already supported by WPA supplicant.