Is there a good assembly drawing somewhere for the Nano 33 IOT bd?
There is what looks like a metal clip with a piece of wax in it on the sub-board with the Wifi/BLE device. Is it a clamp or connector for an external antenna? The device claims to have a built-in antenna.
It's not a connector. It's the u-blox NINA-W102 module's integrated antenna itself. The "wax" is a bit of glue added to provide mechanical support to make it more likely that the fairly delicate antenna can survive the rough treatment it will receive from the average Arduino user.