Yes, there are commands that allow you to add u-boot to the SD card after writing the main image. This is described in the documentation on the Armbian forum in the corresponding topic. But I recommend restoring the regular firmware to eMMC and using the regular u-boot from it. This guarantees normal system operation and the ability to install Armbian in eMMC (while maintaining the ability to use regular tools for working with USB Burn Tool firmware in the future ).
I do not recommend using this option.
The problem of incorrect color has long been solved for Armbian and Libreelec, nothing needs to be deleted from eMMC. This is very bad advice to remove u-boot from eMMC.
Because from the factory, all samples come with a built-in u-boot in eMMC and with standard use (without idiotic tips for removing u-boot from eMMC), you can run Armbian and Libreelec from any external media (please note - including USB) without having to kill your device (remove u-boot). At the same time, you save the regular firmware in eMMC and at the first stage (when you evaluate all the features of new systems), you do not risk anything, just launch any system from an external media, study it, try its functionality. And only after you have found and completely checked all the functions you need on an external media, only after that, you start the automatic procedure for installing the system in eMMC (which itself will correctly install the system in eMMC). Why kill your system (remove u-boot from eMMC) if you don’t know if the new system is suitable for you or not (i.e. you are forced to kill your device just to look at new systems) ?
All Khadas products come with built-in u-boot in eMMC from the factory, and Armbian and Libreelec systems are ready for use on Khadas products, if users are not given stupid tips on removing the built -in u-boot.
And it will fail because these u-boot versions contain errors and cannot work properly with any media.
Wrong advice. The main core works fine with the correct colors with the regular u-boot in eMMC. You need to use the launch system correctly.
There are no problems (if you do everything correctly), this is confirmed by the work of Armbian and Libreelec
For all. Don’t give wrong advice if you don 't know how Armbian and LIbreelec work.