Adapting for ATMega4809 = Arduino Nano Every

[X-Berger]

I would like to use this library for the ATMega4809 but I can't figure out, how to define the USART-Registers
#define UCSRnA UCSR0A // Control and Status Register A
I have found the Register Summary for this chip but Status and Control are different signals:

If it's possible and with a little help, I would add the definition, test it and commit it here.

THX.