I've found a workaround to enable full immersive mode in all apps or on an app-by-app basis. This workaround has two downsides: The camera hole covers the normal status bar as well (the battery value in percent is hidden) and it requires a magisk module which can be a security risk. Here's how to do it:
Open Magisk, select "Downloads" in the side menu, search for "None Display Cutout" and install it
go to Settings>System>Developer Options>Display Cutout and select the new option "No display cutout - MlgmXyysd"
install any app which can control immersive mode (I like "System UI Tuner") to enable immersive mode or enable it only for some apps
To partially fix the statusbar go to Settings>System>Statusbar and enable "battery level in percent" next to the symbol
With root alignment can be further improved by cpadjsutor. For me the ideal offset is 16
It's a bit cumbersome, but chances are this feature will be integrated into a future version of the ROM
This is a copy of e.g. frameworks/base/packages/overlays/DisplayCutoutEmulation* with some changes to make it None. We could create a copy and ship it in the tree or suggest it upstream.
Decription copied from https://forum.xda-developers.com/showpost.php?p=83060959&postcount=561
Repo of None Display Cutout: https://github.com/Magisk-Modules-Repo/noneDisplayCutout