Mac Mini as a music server

I recently re-purposed an old Mac mini (2010) to server duty and have been pretty happy with the outcome. I'm using Asset UPnP in conjunction with either Hi-Fi Cast or BubbleUPnP apps for control to a Chromecast Audio. Works and sounds great. Just ordered a Sonore microRendu (Christmas present to self) which should arrive next week. 

I had a Mac mini in my audio system for several years before exploring other options. I replaced a 2010 model with another in 2012. The 2012 model was spec'd much higher .. I went all-in .. quad-core i7, 16GB RAM, 256GB SSD. I have a license for Audirvana +, Amarra Luxe, JRiver, HQPlayer, and Pure Music. They all have strengths and weaknesses. (Personally, I'm fond of the Amarra sound quality.) You can tweak the settings to your hearts content for each (less so with Amarra) if you so enjoy. You can't go wrong with any of these IMO. That being said, I grew tired of the endless cycle of Apple updates breaking something audio related. It can be very frustrating when, say, a USB driver is suddenly useless. Of course, one can just ignore the updates and leave everything as is but in my case, the Mac mini was also my every day computer and keeping it updated was important to me. 

Nearly 3 years ago, after said frustration, I decided to try a streamer and purchased a Bluesound Node 2. Easy to set up and use. Stable. No more Apple nonsense. Not that Bluesound is without some issues either, but they are normally quick with a fix. A streamer is nothing but a purpose-built computer and Bluesound's Node 2 (or the current 2i) is a nice affordable ($500) solution. However, it's not the utmost in sound quality. Paired with a better DAC, it shines.

As of late I've moved in a different direction entirely with UPnP and re-purposed my old Mac mini as mentioned earlier in this thread. After purchasing a new router (mesh type) I finally ordered a Sonore microRendu ethernet to USB renderer. I'll just say I'm very happy with this approach.

So, there are many options for you, the Mac mini being a very good one. My advice to you is to wait a short time before applying any updates Apple will inevitably offer. Check online for problems before you do anything. Apple's own support forum and various audio forums should give you enough of a heads-up. Best of luck to you.

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.