Can I use USB pins on Pinnacle 100 to connect to Ethernet via an adapter?

Answer

This is not possible, the NRF52840 supports USB device only. To support plugging an Ethernet adapter into it, it would need to support USB host.

There is an option to enable networking over USB, but the Pinnacle would need to be plugged into a Linux machine that can pass internet to it.

https://docs.zephyrproject.org/latest/connectivity/networking/usbnet_setup.html?highlight=usb