Mmm ... I think that WiFiClientSecure library is specific to ESP32 ... on UNO R4 WiFi you have the WiFiSSLClient ... you may need to modify the library that depends on WiFiClientSecure.
I tried changing the board to ESP32 - Arduino Nano and it compiles without problems so I think i have to find a workaround (maybe implementing everything by scratch as I will use some POST and GET APIs).
I have some experience with ArduinoHttpClient which worked fine in past for me when everything was in HTTP, I hope I won’t face a lot of problems when working with HTTPS