Re: AJ6CU 5 inch enhanced nextion file question.
To the best of my knowledge, the KD8CEC Nano firmware on the Raduino is based on the uBITX version, type of display, how and what is connected, and not on the size of the Nextion display. You should be able to select the file from Dr. Lee's Github page:
Please read the FileNameInfo.txt file in the corresponding zip file that matches your version uBITX to help in picking the correct one. There are really only 2 versions of Nano code: 1 for pre-v5 uBITX, and 1 for v5 (also works with v6).