I connected my external USB HDD to try out some 4K movies - everything works fine. The only problem is that the TV's inbuilt software does not allow you to adjust the position of the subtitles nor the color. The subtitles are in very bright white, which is a distraction on dark scenes.
Is there some way to reduce the brightness and or change the color of the subtitles?
I might go for a FireTV 4K later on with Kodi in future which could perhaps be a better way to watch movies.
What? It does. I changed all the things you mentioned on the internal player. Check settings again. I'm watching a movie right now so can't guide you exactly how, but it won't be too tough. Pause and look around. It's there for sure.