Adding my voice to the choir. Could not get any audio from Plex Desktop app for files that had E-AC3 audio after a fresh install of Windows 11. The linked updated mpv dll resolved that for me.
I will say formerg might be on to something, though. The built in Windows Media Player also fails to play audio from the same E-AC3 mkv files. After driving myself nuts for a while, I installed VLC to test it. VLC has no such problem and plays the audio fine.
