Camera App from my Xiaomi Mi 11 Ultra (SKACNXM-13.0.13 stable) is stored in: /system/priv-app/MiuiCamera
I copied it with Mixplorer from my phone and uploaded it to Mega. (package name: com.android.camera - version 4.5.000250.6 from MI 11 Ultra Android 12 - SKACNXM-13.0.13 stable)
But I am sure it's not installable by apk installation - because overwrite apk files from system apps is principle permitted.
And some system apk files has no install runtime at all, because they are just placed in the Rom.
If you have Root, you could try to backup existing apk and then replace the original apk in this path, but I wouldn't do that.
Or creating a Magisk module which replace it systemlessly.
But I think all together wouldn't work because this apk file is dependent on several libraries which are placed, connected and symlinked.
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Good to know, how to extract Rom files, thanks