This is all working as expected. You cannot ssh to a multicast address. More generally, you cannot set up a TCP connection to a multicast address. So that expl

This is all working as expected. You cannot ssh to a multicast address. More generally, you cannot set up a TCP connection to a multicast address. So that explains why your first ssh attempts failed. And as you noticed, ping on macOS is IPv4 only, hence the "Unknown host" error, because it actually tries to resolve "ff02::1%en8" as a host name, it doesn't even recognize it as an IPv6 address. You then ping6 the multicast address and get replies back from all nodes in the multicast group, which includes your MBP. You then ssh to the link-local unicast address fe80::something, which finally works.