I was working on blog article for our site about usage of Armbian extensions and I would be glad if it could be useful for the community
It is on https://github.com/pavlot-scriptec/scriptec-blog/blob/main/customize_armbian_image_using_extensions.md
Also I have created extension to enable Waveshare 3.5 TFT displays for RPi (and maybe other platforms).
Any feedback is wellcome