Trouble with Arduino Nano Every and radio transmission using RH_RF69.h
The Nano Every uses an ATMega4809 processor, so it is different from most Arduino's. It could well be that it isn't supported by the Radiohead library.
The error you shortened to [BlaBlaBla...] could possibly give more information on that.
A full list of what is supported by the Radiohead library is here; you should check if the Arduino Nano Every or the ATMega4809 is on there; alternatively, all the #defines for the supported boards are in the header file.
If it turns out your board is not supported, you could ask the library's authors if they would consider supporting it, or you could use a different board (it should work with an Arduino Nano 33 IoT, I think, but please check first).