jRiver id for FLAC storage and playback?

How about instead a Raspberry Pi with Volumio?

I am using JRiver playing FLAC files via my iMac with an external SotM Dac.. I believe JRiver now has an App for iphones and Android. I have never used Tidal. 

Confusion in your question.  First you say USB to DAC.  I assume you mean computer to DAC through USB.  Then you say SHORT of connecting computer to DAC.  Presumably JRiver is on your computer.  It an be controlled by your phone using Gizmo, JRiver's free app.  Try it.  If you need more there's also  a JRiver pay app.

Sorry, you are right, it doesn’t look like you interpreted my question correctly due to my wording.

By USB to DAC I mean connecting, let’s call it the media server, to the DAC.

When I say “short of connecting a computer” what I meant was a full, generic, multi-purpose computer like a PC or MAC.  In other words, I’m interested in whether there is a more simple and cost effective purpose-built media server that is not a PC or MAC.  The JRiver id being one example solution (it is a purpose built piece of hardware that serves to run the player software and be controlled by phones).

hope that helps to clarify.