From another thread. @Wing_Lee
In Lumin app, disable Custom Re-Sampling, and unused outputs.
If you don’t need AirPlay or Spotify, please disable Lumin Streaming and Spotify Connect respectively.
In Roon, set MQA Capabilities to Render Only or No MQA Support (if your DAC is not MQA).
If you have DSD128 or DSD256 music, you will have to use USB. For other music, you may try both connections and see which sound better to you. Disconnect USB first before you listen to coaxial.