Hi,
I come from a family that has english not as primary language.
I Have a Plex Mediaserver, loaded with Movies etc. as an adult, my (server) preference, is english audio, and my native tongue subtitles.
I Also have kids, they prefer native tongue audio, and only native tongue subtitles if the audio is not native (eg. english).
It seems impossible to configure this on a per user basis, but this would be an excellent function valuable to a lot of user cases.
Regards,
OhmegaStar