hi i have check this problem
problem only with vendor uboot which stored into emmc
SOLUTION 1 : clean emmc vendor uboot (uboot console: store init 3 or via Krescue → emmc clean)
SOLUTION 2: write mainline uboot dl.khadas.com - Index of /Firmware/uboot/mainline/ into EMMC
SOLUTION 3: write openwrt image into EMMC (for examle via same krescue)
SOLUTION 4: wait new version i will try to fix it soon
PS: 21.02 still not ready !!!