Enable Multicast on Mac?
No IP-address is visible/configured and the status of your en0 is inactive.

Adding a route to en0 is obviously possible though. It's still impossible to ping an inactive interface/unreachable network.

Configure an IP-address for en0 and attach it to a network and you should be done. If you have a second Mac configure the same multicast address and check the outgoing pings from the first Mac with sudo tcpdump -ni en0 host 228.0.0.4.