For info, still an issue with "Armbian_21.08.1_Odroidc2_focal_current_5.10.60"
Resolved by:
apt-get install linux-u-boot-odroidc2-current=21.02.3 # downgrade uboot
nand-sata-install # flash new uboot
apt-mark hold linux-u-boot-odroidc2-current # keep current uboot, until confirmed resolved