I also wasn't sure but the OP does mention using the WiFiNina and WIFIUdp libraries so it would indeed seem most likely that he is using a UNO Wifi R4 rather than a Uno R3. The R4 has a more powerful 32-bit Renesas RA4M1 (Arm® Cortex®-M4) processor which has much more memory and includes a larger number of analog pins than the 6 that are actually exposed on the UNO R4 board as well as other additional feature pins.
There is a discussion here about using the 'not connected' pins, but its not trivial and its one thing trying to implement them in code but quite another trying to make a physical connections to them!
^Using Not Connected Pins on RA4M1 - #6 by KurtE
I did wonder whether the Portenta C33 might be a suitable upgrade:
^https://docs.arduino.cc/hardware/portenta-c33/
https://www.mouser.co.uk/ProductDetail/Arduino/ABX00074?qs=ulEaXIWI0c%2FkaqBZMljOXw%3D%3D
It has an even more powerful Renesas R7FA6M5 processor and although it exposes just one additional analog pin on the edge connectors, a lot more is exposed on the high-density connectors on the bottom of the board, . These pins can be accessed using the Portenta Hat Carrier.
Of course the downside is the cost. An external ADC board is cheaper by a factor of 10x....
I am not sure that I understand the reasoning behind choosing such a powerful processor but then hindering its potential by squeezing it into the UNO R3 form factor. I guess familiarity of board layout and compatibility with shields were factors that outweighed tapping into the full potential of this Renesas chip.