This doc [How To] Downmix Surround Sound To AAC Stereo Properly (using FFmpeg Batch Converter) might be of help.
Ultimately if I your media container has surround sound but your audio system doesn’t then you’ll need likely run into audio issues, especial with low dialogue and loud background.
Others may disagree with me but you can try to adjust the player settings as above to help alleviate but it won’t ever be perfect. Adding a stereo stream would be better IMO.
