Set in IMAGE_CLASSES in templates/feature/<name>/image.inc doesn't work, you can set it in the image or other global conf files as a workaround.
1. setup.sh --machine bcm-2xxx-rpi4 --template feature/ostree,feature/fullmetalupdate --dl-layers 2. . oe-init-build-env 3. echo 'HAWKBIT_CONFIG_FILE = "/buildarea3/cli10/wr-build/LINUXEXEC-19130/build/config.cfg"' >> conf/local.conf 4. bitbake wrlinux-image-small