I’m also looking for a solution. I recently upgraded my audio system from a multi-channel amp to a full HDMI receiver, meaning all of my sound is being routed through HDMI only. I’m considering trying an optical cable (as it was set up that way before) and see if the receiver can pull 5.1 audio that way, as I know I was getting 5.1 in the past. I want to determine if it is a factor of the new cabling situation, or a recent software update from Plex.