Arduino Nano Every Compiling Missing " HardwareSerial.h"

Ive spent nearly 2 days just staring at the screen when the following error occurs, I have fully wiped my Arduino IDE from the computer and reinstalled but the same error continues with a missing library:

Arduino: 1.8.12 (Windows 10), Board: “Arduino Nano Every, ATMEGA328”

C:\Users*******\Documents\Arduino\libraries\RadioHead\RH_Serial.cpp:13:11: fatal error: HardwareSerial.h: No such file or directory

#include <HardwareSerial.h>

^~~~~~~~~~~~~~~~~~

compilation terminated.

exit status 1
Error compiling for board Arduino Nano Every.

This report would have more information with
“Show verbose output during compilation”
option enabled in File → Preferences.

Moved your topic to it's current location as it is more suitable.

Could you take a few moments to Learn How To Use The Forum.
Other general help and troubleshooting advice can be found here.
It will help you get the best out of the forum in the future.

The Nano Every is not based on the 328P chip, so Board: "Arduino Nano Every, ATMEGA328" does not make sense to me.

And the RH library is, to my knowledge, written for AVR boards (so not for the Nano Every).