1. To install in eMMC you need to use another command "/root/install.sh" (before running you need to switch to root "su -"). In this thread it was discussed many times.
2. Try to connect SD card with Armbian and run with it. If the system can be run in multi-boot mode, you can either completely erase the internal memory and then you can earn program the firmware via USB. Either you will be able to immediately perform the correct installation of the system in eMMC.
