I have "x96 mini" TV box with seemingly broken eMMC chip (unable to write firmware by USB). S905W SoC. First I've tested if it can boot from SD-card, made with Amlogic Windows utility "Burn Card Maker". The answer is: yes (see the logs below).
Second, I've followed the manual. I've copied the file 'u-boot-s905x-s912' to 'u-boot.ext'. I also edited the file 'extlinux.conf', pointing it to 'meson-gxl-s905w-p281.dtb'. The result is in the logs.
The question is: how to boot the device from the SD card? Should I use somehow the original's firmware u-boot (as it works with the the factory firmware)? The SD card was made with 'Balena etcher'. Armbian image was build from gitub repo ("Armbian-unofficial_24.11.1_Aml-s9xx-box_bookworm_current_6.6.62_minimal.img").