We "fixed" it with broadcast, it was the only way. There are indeed a number of old routers out there that do not work with mDNS well. This is still a problem,

We "fixed" it with broadcast, it was the only way. There are indeed a number of old routers out there that do not work with mDNS well. This is still a problem, but most <5yo routers seem to handle it okay (with the caveat that there are a number of cheap APs and extenders that are completely broken at basic TCP/IP when clients switch). We use broadcast for device-to-device discovery, vs device-to-phone. It makes for noisy networks, but works better than mDNS on a wide range of hardware.