Stereo Downmix not working in Jellyfin media player

[TheDreadPirate]

I'm assuming you are talking about the downmix algorithm settings in Dashboard > Playback > Transcoding. The menu context should hint that they are only applied when transcoding occurs. In JMP, if you are setting the max audio channels to stereo, it will locally downmix and does NOT apply any audio boost or downmix algorithms in a default configuration.