Two old MXQ Pro Amlogic boxes - which version to use?

S905X and S905W are ARMv8 chips but it's common to see 64-bit kernel and 32-bit userspace on Android devices. The older LE11 (arm) image uses the same combo. LE12 and newer now run 64-bit kernel and 64-bit userspace (aarch64). The userspace change is not the reason why the older image boots and the newer one doesn't; it will be something lower level, and the only real way to understand what is or is-not happening is to see the initial u-boot and kernel boot stages via the serial UART log. That requires you to have a USB UART adapter and the UART pins to be physically on the board to connect to - the pads will be there, but cheap boxes often need the pins soldering and they were omitted to reduce manufacturing cost.

Use an official LE13 nightly or image from my test share https://chewitt.libreelec.tv/testing/ as that's the active codebase for dev work. The S905X board should boot with the p212 dtb file in the "box" image. The S905W board should boot with the p281 or Tanix TX3 mini dtb files.