My question is similar to this article , but with a slight difference: it occurred on an SwiftUI Document-based App (DocumentGroup).

Here is my plist:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "<http://www.apple.com/DTDs/PropertyList-1.0.dtd>">
<plist version="1.0">
<dict>
    <key>CFBundleDocumentTypes</key>
    <array>
        <dict>
            <key>CFBundleTypeExtensions</key>
            <array>
                <string>abc</string>
            </array>
            <key>CFBundleTypeName</key>
            <string>ABC File</string>
            <key>LSHandlerRank</key>
            <string>Owner</string>
            <key>LSItemContentTypes</key>
            <array>
                <string>com.xxxx.abc</string>
            </array>
        </dict>
    </array>
    <key>ITSAppUsesNonExemptEncryption</key>
    <false/>
    <key>UTExportedTypeDeclarations</key>
    <array>
        <dict>
            <key>UTTypeConformsTo</key>
            <array>
                <string>com.apple.package</string>
            </array>
            <key>UTTypeDescription</key>
            <string>Scale Data</string>
            <key>UTTypeIconFiles</key>
            <array>
                <string>appicon</string>
            </array>
            <key>UTTypeIdentifier</key>
            <string>com.xxxx.abc</string>
            <key>UTTypeTagSpecification</key>
            <dict>
                <key>public.filename-extension</key>
                <array>
                    <string>abc</string>
                </array>
            </dict>
        </dict>
    ...
    ...

After setting up the icon (the image file, named ‘appicon.png’, is located in a project folder rather than in Assets.xcassets, and only ‘appicon’ is required in plist), the following issues were encountered::

1. The simulator’s document file shows the icon, but the physical device does not display any icons.

2. Deleting Xcode’s Developer Cache, Derived Data, Build, and restarting the Mac — Ineffective

3. When the physical device installs a new version of the app for the first time, and there are no older versions of the app on the device, the icon appears successfully — Effective

4. Deleting the old version of the app on the physical device, restarting, and reinstalling the new version of the app — Ineffective

5. On the iPhone, long-pressing the document file of the physical device and selecting ‘get info’ — Effective

6. Using the above method on the iPad version — Ineffective

7. It was found on StackOverFlow that Mac has a similar issue, which can be resolved by clearing the cache via Command Line to update the icon

8. However, since iPads do not have Command Line, the next idea was to Reset All Settings for the iPad + reinstall the new version of the app — Effective

Hope the information and steps provided above can help everyone.