I just got the 900h (amazon prime day). Did a lot of research before getting this tv and have found the same results - for some reason the plex app (on the tv) will not send ddthd or dtsma via earc. Not sure why. Even though the tv manufacturers say it will. What I was told this is in regards to hooking up a set top player (e.g. Shield) to your TV and then hooking up an HDMI cable to the arc input of the TV that goes to your receiver. In this case your set top box will send dtsthd/dtsma through your TV and into your receiver. I fail to see the logic in this since I would just hook up the set top box directly to the receiver. If those other apps on your tv are doing it then I guess it’s just a plex thing. I guess if thd and ma is paramount to you, get a Shield and bypass the tvs smart system altogether.