Just wanted to add my tuppence 'orth that yep, it looks like Sammy 2018 or newer TVs have ditched DTS support (including passthrough via ARC) which is a complete pain in the arse! My 2017 Q9 had it but my replacement 2019 Q90R, nope!
So, in terms of using TV ARC to my HW-N950 soundbar and the TV's Plex app, well that's gimped for playing DTS movies, as is going the Chromecast route..
..and in terms of plugging a media player like an XBox One or a PS4 directly into a compatible receiver/soundbar, both the XBox One and PS4 don't allow 3rd party apps like Plex to access DTS passthrough for one reason or another (after a bit of searching I found that its a known thing that Microsoft don't to allow passthrough to be used by 3rd party apps, even though it's apparently been in testing for ages and it seems like Sony don't either..)
Sooo, if you want a single streaming box that supports all your audio formats and assuming you have a compatible receiver or soundbar then you're going to have to try and source something like an Nvidia Shield TV instead (I'm probably very late to the party, but quelle suprise they're getting harder and harder to source)...
A real shame in this day and age of people having Smart TVs and probably one or more multimedia consoles in their living room set-up that are all
meant to do the same thing but actually, don't cover any of the bases fully at all..
..still, as someone mentioned earlier in this thread, market research probably flagged this flexibility of audio support as niche and not worth the continued investment in licencing or support