I decided to spend some time looking into this, for the time being.
At first I was gonna use my WDTV Live, but for some reason it doesn't like browsing its own DLNA server list and will result, just by flipping thru different selection options..
So I decided to try my Samsung BD-E5300 Blu-Ray Player. Figured its Samsung, and its not too old, so it should be pretty decent right?
Well, I get mixed results even using the Samsung Profile.
I pretty much have to use the Mpeg Mimetype Override to get anything working, as far as my MKV's go. Most of them are a mix of Xvid, Mpeg4 AVC, etc, even if its set to Never Convert, or Convert Always, or Convert Unsupported.
So the MIME override gets my files to at least show video. But so far I can't get anything other than videos with an AC3 for a primary audio track, to play any audio. It always comes up unsupported, no matter what conversion strategy or format I use.. FLAC aside, this player should be able to play MP3, AAC-LC, etc.
Interesting note. The player seems to ignore the Video DLNA: Override info even when its changed to gibberish.
I don't know why the player ignores even converted audio (assuming its being converted), but I played my FF7 OST which is FLAC and that worked fine so I assume Audio conversion at least works..
I don't know if this will help the Dev team at all. But those are my observations.
edit: I did a speed run through the Menu on my WDTV, and it appears to play anything I throw at it, even shows multiple audio tracks, etc.
Clearly this is a device support issue, but I hope any of the info helps, for workaround ideas, etc.
I might be willing to loan the BD Player out if you return it in a timeley manner, so you can study its idiosyncrasies - if you wish.