@kszaq
EDIT: So, I couldn't get my Khadas VIM to accept the latest 8.1.9 upgrade from 8.1.8. The first time, it succeeded and went to reboot, but before the boot logo would come on, the box would turn the power off. Any subsequent boot attempts with the SD inserted resulted in immediate power off (no boot logo). I setup a fresh SD with 8.1.8 and booted it succesfully. This time I tried the update again, and the same thing happened, however - I can no longer BOOT ANY SD card based OS including Linux, earlier LE releases, etc. All of this stuff worked fine a few hours ago.
At first I thought the card slot might be fried, but when I loaded up Android, I was able to see the SD card, format it, copy files to it, read files from it (installed a few APKs as tests). I just cannot boot from it anymore. Same with USB (not sure if it was possible on the VIM).
I have tried wiping the EMMC clean, and re-burning the Android version with Amlogic burn tool.... successfully, but the same results when trying to boot SD Libreelec. Sometimes it will just sit at the "Khadas" boot screen forever, and sometimes the boot screen doesn't show up at all (just black screen). As soon as I take out the SD card and reboot it, it boots up fine and Android will load up. I can then put the SD card in, and it works inside Android....
I really don't know what the heck happened, or how on earth to go about trying to remedy this. But it seems like a bit of a coincidence that the SD stopped booting, right when I was applying the latest 8.1.9 update. I repeat... it works inside android (the SD slot)
I am totally out of ideas!!