It does not matter if you turn them ON or OFF.. THEY ALWAYS ARE ON AND ON FOR EVERY APP! These global captions over ride any caption settings you have on Amazon or Netlflix now. I am writing this in 2019. but worse your Roku captions have now turned into being unreadable. Unuseable fonts! If you were to override the other apps captions then.. it might not be so worthless had yours been workable! but yours are see thru. Transparent. The image on the screen covers the letters. Ridiculous. I call this plain and simply careless and discrimination. People depend on the captions and you don't care.
My old Rokus allow background to be set to opaque
And they still function globally.
The Expresst + I bought through an upgrade promotion failed to override channel captions, so I went back to my old Roku.