Mac Mini as a music server

You can disable updates on a Mac. Go to App Store and uncheck the "automatically check for updates" box.

Sure, but when you turn automatic updates off, security updates aren't installed. If streaming or internet radio are part of why you use the Mac, you become more vulnerable to attack every day. You get annoying prompts daily suggesting updating. Most updates bloat the OS with crap neutral or detrimental to audio playback. ITUNES never goes away and it opens every time you load a disc even just to rip it. 

My trouble with Audirvana+ mostly boiled down to library indexing hidden files getting screwed up. This causes library appearing totally gone when it really isn't (scary!). Support is by one smart busy guy in France...replies are friendly but take a while. The fix usually entailed finding hidden files, deleting them, reinstalling, then reloading library which took almost a day for me with about 3TB of music at the time, connected directly to a Lacie Firewire drive, not across a network. It wasn't the worst audio trauma I have dealt with, but why bother?!!
Cheers,
Spencer 

Do you think it stems from Apple's penchant for not providing ancillary vendors pre-knowledge of impending changes/updates & the subsequent lag as the ancillary vendor "catches up" to make their program compatible?

Yes, absolutely. Over the years each and every music player program I've used has been impacted by an Apple update. (I have licences for Amarra, Audirvana+, BitPerfect, Fidelia, HQPlayer, JRMC, and Pure Music.) Very frustrating indeed. From my experience HQPlayer has seen fewer issues than the others. Eventually the problems get fixed, for the most part anyway. I stopped using Pure Music entirely after one such update .. the problem was never resolved and I gave up. Don't even get me started on Amarra!

Of course the easy option is, as @thaluza mentioned, to turn off auto updates but I'm with @sbank on this one. 

I've been running Roon on my 2012 mini for about 5 years. It feeds an Allo USBridge in another room which in turn feeds my NuPrime integrated. I haven't bothered to update the OS in quite some time. I use it strictly as a music server. It is always on and functions beautifully. Everything sounds great. I'm actually considering buying another one now to have ready when this one inevitably dies.