Emre,
Thanks for replying. The time capsule is connected to a switch and my iMac is then connected via wireless network to the Apple Time Capsule. Currently, the ROCK Nuc is in another room with my audio system. I am able to play music on the system by leaving the Nuc plugged in via USB to the McIntosh preamplifier even though I am not using the Nuc computer as the Roon Core.
Your message got me thinking. I have the iMac connected via wireless most of the time but also have an ethernet cable attached to it that runs into the same switch that my Nuc does. When I tried to use my iOS devices to control the audio to my preamplifier, the iOS app would only see the iMac as the core if my iMac is connected via wireless and the Roon app is open on the iMac. When switched to ethernet the iOS devices do not see the core.
It seems that I can switch from the wireless network to ethernet if I use the iMac macOS Roon application to stream to my preamplifier even though the iOS devices are then not able to connect. It is just all very strange as I have probably run this ROCK core through ethernet like this using 1.7 for a year with not a single issue.