Yeah they respond. `ping mdns.mcast.net`, shows responses from ip addresses I recognize on my LAN, `arp -a`, still no hostnames. Tried all the other suggestions online too. Tried on my Mac and Rpi, same network, just a single ethernet LAN.

Router is all default except that I port-forwarded something. Funny enough, it sees the hostnames. I'm guessing it's some problem with both my computers, but no real need to fix this because I memorized the addrs already.