Thanks for your suggestions so far.
I built an image using the following parameters (see end of post) and now it boots pure uefi:
This seems to have created an sdcard image without the u-boot after dd command, because now I got a grub menu and still booted the old EMMC system but without the system finding any traces of u-boot to kick-in.
Not sure about =uefi-arm64 as it seems to be too generic:
vs rock-5-itx seems more accurate: https://github.com/armbian/build/blob/main/config/boards/rock-5-itx.conf
I used the following in my compile command :
This is a sample command that worked for me. Now I am running from sdcard with a pure uefi boot using my custom Armbian build.