No cable is the best cable

[CongoFather]

Petter, if I've understood correctly, you have Roon core on an iMac, and want to stream to a D250. First, uninstall and forget about AIR3 on the Mac, you don't need it, it's built into Roon. Throw away all that regen stuff too, and just use vanilla ethernet cables. Make sure all firmwares and softwares are upto date. On the iMac, disable app-store, software updates, and spotlight. If both the D250 and iMac are on the same network, you should see it in Roon Preferences > Audio, it'll be listed twice: one RAAT, one AIR. Select, and enjoy. There may be a dropout problem with a gigabit cable, older 100baseT cables are recommended. Otherwise try WiFi. If you still have bad dropouts suspect your network router. Otherwise, I've found Devialet/Roon to be extremely good. It's about as simple as it gets, honestly.

I experience no dropouts when I use Mac Mini with CAT7 cable over Gigabit ethernet switch(sotm SNG-10G). Devialet220 is also connected to the same switch with Supra CAT8 cable. This SOTM switch is connected to another switch(Ubiquiti Edge 10x switch) with fiber-optic cable. My NAS and internet router are also connected to Edge Switch 10X with CAT-7 cables (which support gigabit ethernet connections)..

No matter what kind of driver I use(Roon RAAT, AIR Ethernet(for Roon and Audirvana)) on Mac Mini, I do not experience any dropouts.