This is some strange looking output. What software are you using?
#define RTC (*(RTC_t *) 0x0140) /* Real-Time Counter */
Rename the RTC variable, RTC is already defined in <avr/iom4809.h> (but not in <avr/iom328p.h>).Code: [Select]#define RTC (*(RTC_t *) 0x0140) /* Real-Time Counter */
That's probably because the atmega4809 has an internal RTC, although I'm not sure how accurate it is.
Is there a way to verify a library for the new Nano boards without installing by trial and error?
By "installing by trial and error", do you mean the process of installing a potential library, uploading to the Nano, and seeing if it works?