Good news.
Thanks to the work of many, there is now a real opportunity to run the Armbian system with the main core on Jetson Nano, and more importantly, it is easy to integrate the image build process into the official GIT Armbian. In the near future, I plan to post ready-made images with the latest kernel 5.10.22 on the download site. To run them, you need to update u-boot to Jetson Nano. This is very easy to do, just run the latest official version of Ubuntu for Jetson Nano from the SD card, it will update itself in SPI (?) u-boot to the latest version (2020.04), after that you can run Armbian from any SD card or USB media. The new u-boot supports automatic system startup from both media or over the network. Also, now you can build an Armbian image for Jetson Nano yourself, easily build the latest kernel with the necessary options, etc.
https://users.armbian.com/balbes150/
https://mega.nz/#F!j9QSDQSQ!6WpasOlbZYIInfw6yo4phQ
https://disk.yandex.ru/d/XBRXnig7F1M4rw?w=1