1. Did you edit uEnv.txt file for aml and correct FDT in BOOT partition?
2. Did you apply u-boot with
sudo dd if=u-boot-odroid-n2.img of=Armbian_19.11.5_Arm-64_bionic_dev_5.5.0-rc7_desktop_20200124.img conv=notrunc bs=1 count=442
sudo dd if=u-boot-odroid-n2.img of=Armbian_19.11.5_Arm-64_bionic_dev_5.5.0-rc7_desktop_20200124.img conv=notrunc bs=512 skip=1 seek=1