On a slight tangent, mDNS had turned into an absolute nightmare for me. I must have tried 5 different FOSS Raspberry Pi streaming OSs, none of which did the Spotify cast integration actually work on, until I finally figured out it's because it's using mDNS and my router (despite being purchased in 2023 for $200) didn't support mDNS. There's also a bunch of other services (like Home Assistant) that just assume you have working mDNS and point everything to <appname>.local

I finally figured out where the service file was, and changed it to IP, and now it works.