Yes I know and thats no big deal, since I`ve already set up the cross-compile environment on my Ubuntu PC, (or even compile the kernel directly on the box which takes only 15-20 minutes).
I've compared the .108 and .99 .configs from your images, but they are completely different, so no idea where to start...
I also compiled the mainline Kernel (4.18.rc8) from here https://git.kernel.org/pub/scm/linux/kernel/git/khilman/linux-amlogic.git/?h=v4.19/integ
Boots and works fine so far, but like all mainline Kernel, no HDMI-Out with the S812, thus only useful for server OS.