I don't see an option anywhere for that on mine with MIUI 14.
On that video from
@VidJunky I think he was saying it was built in to the Chinese rom of a previous version and it could be extracted on the Indian version. I don't know.
I also don't know what region of the World you are in and what version of MIUI you are on, or I missed those. I suspect the 9C didn't go much higher than MIUI 12.
How is it affecting your day to day use, apart from not liking the screen? I don't completely understand the problem.
Do you see Wallpaper Carousel?
Without having your device there's little way to know how to turn it off, and your information is too succinct / short. Sorry.
Possibly that Screensaver is also only a feature only on LCD screens, not Amoled.
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Also there's a search bar when you open settings, in case one of us mentioned the App Drawer to search for Screensaver.