Problem existing since minimum the beggining of 2021.
I have the same problem :
- On my Samsung Q60 2019 TV → No problem
- On my Samsung Q80 2021 TV → Problem
The two TV have the exact same OS version and exact same Plex application version.
This problem is already explained in many tread and even on the Samsung forum. Here some example and it took me only 1 minute to find them…
[Problem with audio language with Samsung Smart TV]
[Samsung AU9000 wrong audio track played though is selected correctly]
[Only playing english language]
[PLEX on TV Samsung QE55Q70A doesn't switch audio tracks in a movie]
It’s time to find a way to resolve this WITHOUT :
- Disabling direct play
- Reencode all our moovies
- Replace our TV
- Buy another external device on which install plex
Etc…
Many thanks… 
