I’m testing NuttX on Atmega128A using the BK-AVR128 board.
I found the board schematic here:
https://blog.naver.com/eziya76/221248746834
I bought the board from Aliexpress: https://aliexpress.com/item/1005006234334573.html
This board uses UART0 that means pins PE0 (RXD) and PE1 (TXD) as serial console.