Thank you very much for your support and patience. I would rather try to do your first option, install your next version come with 4.20 kernel. But I have no idea what keyword I need to search with to get to the page that mentions how to install system on S9xxx. Can you give me the direct link or some tips/steps that I can use to follow up? Moreover, is there any chance that we can re compile your source to boot from eMMC and pack it to img file( with all uboot, fs, dtb and everything) then flash it like a normal android image via usb download tool?