Then I try:
./compile.sh docker KERNEL_ONLY=yes BOARD=duo BRANCH=current KERNEL_CONFIGURE=yes
[ warn ] The KERNEL_ONLY key is no longer used. [ KERNEL_ONLY=yes ]
[ warn ] Instead, use BUILD_ONLY to select the build target. [ u-boot,kernel,armbian-config,armbian-zsh,plymouth-theme-armbian,armbian-firmware,armbian-bsp ]
[ o.k. ] BUILD_ONLY enforced to: [ u-boot,kernel,armbian-config,armbian-zsh,plymouth-theme-armbian,armbian-firmware,armbian-bsp ]
/root/armbian/lib/functions/main/config-prepare.sh: line 109: /root/armbian/config/boards/duo.: No such file or directory
[ error ] ERROR in function prepare_and_config_main_build_single [ functions/cli/cli-entrypoint.sh:106 -> functions/main/config-prepare.sh:112 -> functions/logging/traps.sh:0 ]
[ error ] Board configuration does not define valid kernel config
[ o.k. ] Process terminated