Right, Allwinner T113-S3, a new beast for our friend! RT-Thread Studio, that sounds both intriguing and potentially headache-inducing. Eclipse and GCC after a decade of KEIL and IAR? A jump for sure! Bare-metal ARM926 experience will probably help, somewhat. I remember once wrestling with a completely undocumented microcontroller while trying to build a custom weather station. Getting the SPI interface to work correctly felt like scaling an impossibly steep Slope Game. Good luck to our friend, it's a journey.