Getting App not installed error when I tried installing from phone storage

Question

App not installed error comes only when I try to install the APK file from phone's file manager. When I try to install the same APK with adb install <name.apk> it works.

Here is the AndroidManifest code

<uses-permission android:name="android.permission.SYSTEM_ALERT_WINDOW" />
    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
    <uses-permission android:name="android.permission.INTERNET" />
    <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:isSplitRequired="false"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">

I made sure:

1. No other versions of the APK installed on the phone
2. No APKs installed with the same package but different signature
3. Play Protect was completely turned off.
4. No other package verification going on since my phone has Oxygen OS (Not MIUI or something)

Working solution:

Only through ADB but I want it to install from phone memory then only I can share the APKs with others. I had also tried on several other devices but the same issue. That's why I believe something going on with Manifest.

Help will be much appreciated. Thanks in advance.