...Ugh!
I hate to say it, but it looks like the PS4 is less equipped than I thought: It fails to play any of the files in the one 5.1 FLAC album. Detects it as a playable file and tries, mind you--just fails (the APE's and MKA's don't even appear).
However, the issue isn't that they're FLAC files; it's that they're 5.1 surround. It doesn't make any darn sense to me that they wouldn't offer such functionality in an app on a console capable of taking 7.1 LPCM for games and movies, but it would appear that Sony's Media Player only supports 2-channel audio.
That being said, suspecting this, I went ahead and converted one of my 2-channel files (an MKA containing PCM, 96/24) to FLAC and the resulting file played back just fine.
I think there's still a case to be made, since the vast majority of anybody's music library is going to be 2-channel audio anyway.
And no, unfortunately: The PS4 does not appear in MC's list of zones, so unless there's something I'm missing, it doesn't appear that content can be pushed to it.
For comparison, the Xbox One Media Player--which works just like Sony's in that it can pull--also fails to play APE's and MKA's (containing DTS(-MA) or PCM), but successfully plays them when output mode is set to
PCM 24 Bit (2- or 5.1-channel). It also successfully plays FLAC's (in spite of the format
not being listed amongst those officially supported), even in 5.1--though oddly enough, it sends the audio for the side channels to the back channels.
Interestingly, the Xbox One
does appear in MC's list of playback zones, so one can push to it. Attempting to do so prompted it to open the app store for me to download Groove. I did so, and as with Media Player, it successfully played the 5.1 FLAC's. I'm not sure why it doesn't just open the aforementioned Media Player, but it is what it is.
...I'm sorry. It occurs to me that it might have been worth mentioning that all audio in my setup passes through a Marantz SR-5008 A/V receiver. I don't know if that's particularly relevant to this discussion or not.