The specs for Uno WiFi Rev2 imply that it is similiar to other Uno's with wifi.
WiFiNINA.h
This library allows you to use the Arduino UNO WiFi Rev.2, Arduino MKR 1010 and Arduino MKR VIDOR 4000 WiFi capabilities. It can serve as either a server accepting incoming connections or a client making outgoing ones. The library supports WEP and WPA2 Personal encryption. This library support all the same methods of the original WiFi library plus the connectSSL(). The WiFiNINA library is very similar to the Ethernet and the library WiFi, and many of the function calls are the same.
Using the WiFiNINA.h library only and writing to ThingSpeak using their example json code to Bulk upload works fine.
but ThingSpeak.h does not (yet?) have any code references to enable UnoWiFi Rev2.
It would be helpful if ThingSpeak.h was revised.
Should this issue be raised with ThingSpeak?