I hate to break the news but either way still reverts back to DHCP after a reboot... Got the "x8h plus with "X8H_PLUS_LOLLIPOP_RC2_NEWBOOT.img"(true shutdown) and I even tried a fresh install 18.2 from SD with the dtb.img replaced from 18.0(final) and still goes back to DHCP after reboot/shutdown. Lets wait to see for more feedback as I might have an "Odd Box". When I ran Kodi 17.6, the first image listed = one that booted and worked if that helps.
if you dare , you may also try the dtb from the kodi 17.6 image.
use a spare SD 'cause it may not boot at all.