I was hoping this thread was going to be measurements of AppleTV 4K.
I assume the MiniDSP U-Dio8 is used to interface between Mac Mini USB-out and Genelec AES-in without a redundant AD/DA step, which looks like a good method. Unfortunate that you don't like the sonics. Like others I'm curious about how/why/if that's happening.
I have considered/hesitated mildly about adding a MiniDSP device in the chain, but haven't need to in the end. Some of them measure better than others. I don't have issues using a Mac as a sound source SQ-wise (ignoring the M1/M2 memory thing). I no longer have an AppleTV device but it used to work well (HDMI-out, of course).