The arptables requires but does not provide /etc/sysconfig/arptables. Adding a sample file with a commented out example would help the user guess what is needed there.
Add the file /etc/sysconfig/arptables.
wrlinux-8/wrlinux/configure --enable-rootfs=glibc-small --enable-board=qemux86-64 --enable-bootimage=cpio.gz.u-boot --with-template=feature/package-management --with-rcpl-version=0005 make arptables.addpkg make make start-target login as root systemctl status arptables.service