Since the GUI is not used on the custom board, we disabled the HDMI part (dtb).
After that, I flashed with emmc and proceeded.
In the case of R31.1, it was possible to connect to the consol environment where login was completed without any separate procedure.(default ID: nvidia PASSWORD: nvidia)
In the case of R32.x, the Linux installation procedure occurs with consol. In the process, the password and password input section came out, and the input was completed.