Armbian is not compatible with the device tree built into our firmware until Armbian updates to Linux 6.2+.
The issue is that the SPI firmware provides the latest device tree to Linux. Armbian is designed for an older kernel so it doesn’t know how to initiate the Ethernet port with the newer device tree. You have to get the system to boot from the Armbian firmware/bootloader instead of ours.
Flash Armbian to eMMC and then erase the SPI NOR. Erasing the SPI NOR also erases the built-in firmware and you will have to re-flash via pyamlboot if you want to boot from USB again. This is for experts only. Ideally Armbian provides the device-tree for their kernel version using a standard boot process. This is something you have to ask the Armbian devs to do to avoid the issue.