2GB RAM version has two 8Gb (1GB) DDR4 chips, but the DDR topology data from GitHub (which is used by Armbian for compiling u-boot) is wrong, and it causes failure.
In tim/ddr/DDR_TOPOLOGY_6.txt,
You should change
ddr_mem_size_index=5
to
ddr_mem_size_index=4
since it doesn’t have a single 16Gb chip.