If the tablet won't turn on, you may need to open the back cover and look for a code printed on the green circuit board (e.g., AL_A133_VG_V1.0 Build Number:
: Official firmware often uses older 4.x or 5.x kernels. Modern mainline kernel support is ongoing but stable for basic functions. Allwinner A133 Firmware
The output is a ready-to-flash a133_demo.img . Unfortunately, Allwinner requires a commercial license for the full SDK (approx $2k–$5k), but community support via linux-sunxi.org is excellent. If the tablet won't turn on, you may