Same Problem.

we are moving all the documentation from arduino.org website, and we are currently working on the Uno WiFi pages
thanks for your patience, we will publish the pages ASAP

Found this after much googling...
https://www.arduino.cc/en/Guide/ArduinoUnoWiFi

...I'm guessing that's the new page that replaces:
http://www.arduino.org/learning/tutorials/boards-tutorials/content/arduino-uno-wifi-tutorial

I also found... (but can't actually get my board to firmware update)
https://github.com/arduino-libraries/UnoWiFi-FirmwareUpdater-Plugin

Really frustrating how the tale of two Arduino's was supposedly settled October 1st, 2016 - yet a year later most pages still result in the "You are now going to be redirected to arduino.cc, for more information please read this blogpost."

we are moving all the documentation from arduino.org website, and we are currently working on the Uno WiFi pages
thanks for your patience, we will publish the pages ASAP

It's been over two years, not so ASAP...

@spacelego for UnoWiFi-FirmwareUpdater-Plugin
Will this link suffice for what we are looking for exactly (though its for WiFiNINA), if so I will update the read me file there as well.
https://www.arduino.cc/en/Tutorial/WiFiNINAFirmwareUpdater