Xiaomi's Mi 11 Ultra features a secondary display at its rear but has received criticism for the poor implementation of that feature. That is set to change shortly, as new information indicates that an upcoming build will allow modes like video recording, portrait, and a bunch of other camera modes on the rear display.
https://www.notebookcheck.net/Mi-11-Ultra-rear-display-set-to-finally-get-slew-of-camera-features-in-imminent-update.540603.0.html
Well, it's too small, which in addition to its aspect ratio and location, basically the whole implementation, also makes it ugly. None of that's gonna change.
Generally hardware creators do not have high enough software. Especially with very new Version One of a product. Sony and most other brands have this "feature".
So we prefer mature software coming from software specialists. " Open Camera", & Microsoft Launcher are usually better than OEM software.
This feature is already in the weekly beta software I have on my Chinese unit.
Whilst enable the toggle now on the main preview screen, it shows rear display for all modes including video.
Very useful for subjects to check they are in frame and zoom levels etc. Works well for selfie footage using back cameras.