I tested it and it's fine
./ext-manager.sh add https://github.com/jumkey/redpill-load/raw/develop/redpill-runtime-qjs/rpext-index.json
./ext-manager.sh add https://github.com/jumkey/redpill-load/raw/develop/redpill-qjs-dtb/rpext-index.json
BRP_JUN_MOD=1 BRP_DEBUG=0 BRP_USER_CFG=user_config-ds2422.json ./build-loader.sh DS2422+ 7.0.1-42218 loader.img