OK, I got it to build. The secret is REPOSITORY_INSTALL=
REPOSITORY_INSTALL (comma-separated list): list of core packages which will be installed from repository
Available options: u-boot, kernel, bsp, armbian-bsp-cli,armbian-bsp-desktop,armbian-desktop,armbian-config, armbian-firmware
Set to “” to use packages one from local output or build if not available
I'll do it from scratch and post final instructions.