Some answers here: https://forum.armbian.com/topic/12988-armbian-for-amlogic-s905x3/page/7/?tab=comments#comment-101887
Moreover, on my X96 (Air 4/32Gb version), the most efficient file is meson-sm1-sei610-ethfix.dtb (ethernet speed is fixed at 100Mb because 1000Mb doesn't work on this kind of box).
I suppose that your bootloader in eMMC is broken now and you need to reinstall the android firmware to get to a clean starting point.
For that, you need the stock firmware of your box, USB cable Male<->Male and USB Burning Tool.