arping broken on Mojave

[Richard L. Hamilton]

from a 15"  2017 MacBook Pro:

sh-3.2$ sudo arping echo-dot-lr
arping: libnet_init(LIBNET_LINK, <null>): <no error message>
sh-3.2$ sudo arping crabapple
arping: libnet_init(LIBNET_LINK, <null>): <no error message>

(also with MAC or IP for crabapple, a 2018 Mac Mini also running  Mojave)

Has anyone else seen this? Or  am I doing  something wrong?  Its dependencies are up-to-date;  indeed, I  forcibly uninstalled and reinstalled it and them, no difference. It also fails with the port freshly installed on crabapple.

My main interest is that Amazon Echo devices do not respond to ICMP echo request, but are said to respond to arping (they'd just about have to).