For people with same problem than mine, this is what i did
Install u-boot Debian package, one that you knows works (download via: https://imola.armbian.com/apt/pool/main/l/linux-u-boot-nanopim4v2-current/)
dpkg -i linux-u-boot-current-nanopim4v2_xxxxxx_arm64.deb
Launch armbian-config tool
sudo armbian-config
System -> Install -> Install/update the bootloader SD/eMMC
The SD is now bootable
Thx again to Igor for his help 🤜🤛
