I have the same thing here, on my Roku devices as well as my Roku TV. This seems to be controlled by the various channel apps, which, as you may know, are provided by the channel services themselves to run on the Roku platform. Some channel apps, when going to the screensaver honor your choice of screensaver (mine also it the aquatic fish tank), some just bring up the Roku system default for that Roku, and I've got some that just deliver a black screen.
Roku Community Streaming Expert I am not a Roku employee, only a user like you. Please, no support questions via private message -- post them publicly to the Community where others may benefit as well. If this post solves your problem please help others find this answer by clicking "Accept as Solution.".
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