Unbricking the NanoPi R6S
TL;DR - Run upgrade_tool UL MiniLoaderAll.bin in Maskrom mode. I recently obtained a NanoPi R6S with the intention of turning it into a router powered by OpenWrt. Everything seemed to be going swimmingly well until I tried to expand the SquashFS OpenWrt partition on the internal eMMC storage, and that seemed to brick the device. Every time it was turned on, the red SYS light would stay solid instead of blinking after a bit - that meant it was stuck in the bootloader phase.