Is CoreAudio Exclusive Mode just available when using an external DAC? Or is it possible to use when using a MacBook alone? I can only get the Output to be OS Mixer. But maybe that’s all it ever can be without an external DAC.
Looking at your signal path, you are still outputting to System Output (OS mixer) instead of Built-in Output (exclusive mode). Can you change the zone you output to? (Speaker icon bottom right in the black bottom bar).
Exclusive mode should be available for any device connected to your Core that Roon is controlling directly.
It is not available when playing to System Output, which by definition involves playing to the operating system’s mixer (ie, not exclusive ). Hope that clears it up!