Hi, how are you? Well, I don't know English very well, so this text will be translated using Google Translate since I'm Brazilian. Anyway. I found a way to boot the SD card with Linux on the Allwinner H3 chip, using a Chinese MXQ 4K 5G TV box. I booted Android normally and, using the remote control, pressed the power button and then confirmed. After shutting down, I booted with the remote control and Linux started normally. After that, every time I booted with the SD card, it booted perfectly. Another thing I did before, but I believe it doesn't affect this, was to enable USB0 device mode in developer mode. I hope this information helps with your Linux projects!
