Standard JRiver set up will play DSD files, but converted to high res PCM output. You certainly can’t play any FLAC music through Apple Music or the Files app. It can’t natively play DSD files, and despite FLAC support being listed in the specs since from the iPhone 8 through to the new iPhone 11 models, Apple doesn’t natively support FLAC files.
It’s a high-resolution format that produces a high-resolution signal in a different way to that employed by the PCM system that can be transmitted as WAV, FLAC, ALAC or AIFF.
