If you’re using an Android TV device like the nVidia Shield Pro, I recommend also installing Kodi for playback. It has much better codec support meaning less transcoding (and further quality loss), and there’s a few oddities in the Jellyfin Client subtitle support.

Took me about a day of Googling and faffing about to get everything working and it pumping out all the full quality audio formats to my AVR. Seems that by default it likes putting everything in stereo.