How about adding another audio stream to your Video files with ffmpeg? You could even automate it with a script on a cronjob or make a Jellyfin Add-on. You would first have to detect if there is already a mono or stereo stream. Then invoke something like ffmpeg -i input.mp4 -c:v copy -c:a copy -c:a aac -rematrix_maxval 1.0 -ac 2 output.mp4 (haven't tested this and it would drop subtitles)