Two questions/issues here:
1. Certain apps that have auto preview features make using the app a horrible experience, basically it's unusable. Obviously I have it on for movies in other apps, however when I tune to an app like Bravo, it's such a bad experience because each time you scroll through shows/episodes on the landing page, the stupid auto preview kicks in, which triggers the black screen to match framerates. Rinse and repeat, it's just not feasible. I know I don't need match framerate for shows on Bravo, but then I'd have to turn it off and on each time I want to use an app with it or not use it, etc. I can't turn off auto preview like I can with Netflix, so is this something that can be looked into? Am I going to get the "it's the channel/apps decision, not ours" response?
2. This is from a reddit post:
23.976fps content is now correctly output at 23.973Hz (verified with HDFury Integral 2), fixing an issue present in past Roku Ultra model
24.000fps content is now incorrectly output at 23.973Hz, breaking 24.000Hz output, which did work in past Roku Ultra models
Will 24fps be output correctly in a future update? Apple TV just fixed this in their latest tvOS beta.
1) The "solution" is to disable/enable framerate matching (for now) - at least for those apps that havent been framerate locked. As you discovered, not all apps support disabling preview/auto-preview. Whether its more likely Roku will implement a more granular (per app) framerate control, or Bravo et al. implement auto-preview controls, remains to be seen, but both are likely years away, if ever.
2) One could only hope that pre-4800 models get fixed for 23.976 and 4800+ models get fixed for 24.000, since the likelihood of this being addressed any time soon (if ever) is low, despite Apple's recent though years-belated solution.
Of course, the best solution(s) for all of this is:
1) A framerate API for app usage and/or granular global framerate controls.
2) All services/apps adding full auto-preview/auto-play controls.
Give it another 3 years - and be happily surprised if somehow Roku addresses this within 1.