On macOS, you can choose between two different browser engines to power webviews, as described in this article. Which browser engine you choose may be determined by whether you plan to distribute your app through the Mac App Store.
If you plan to distribute your app through the Mac App Store, then you must enable and use the optional WebKit browser engine backend using the steps described here. The default Chromium browser engine backend cannot be used in a Mac App Store app because Chromium is unable to run in the App Store's sandboxed environment without significant modifications.
If you don't need to distribute your app through the Mac App Store, then you can utilize the default Chromium browser engine backend and distribute your app outside the Mac App Store by notarizing it like described below.
Notarizing an app that uses Chromium
For reference, please see this zip folder, which contains an example notarize-app.sh bash script and entitlements.plist file that can be used to successfully notarize apps that use 3D WebView's default Chromium browser engine backend. Before running this script, you must first update the values of the variables in all caps (e.g. APPLE_ID, TEAM_ID, PASSWORD, etc) to match the details for your developer account and app. After you have populated the script's variables with the correct information, you can execute it via the macOS Terminal app. If the app is notarized successfully, the script's terminal output should resemble the following:
Code signing...
./build-mac.app: replacing existing signature
./build-mac.app: signed app bundle with Mach-O universal (x86_64 arm64) [...]
Creating archive...
...
Uploading to the notarization service...
...
Successfully uploaded file
id: {submission_id}
path: /Users/example/archive.zip
Waiting for processing to complete.
Current status: Accepted...............
Processing complete
id: {submission_id}
status: Accepted
Removing archive...
Finished notarization. Next, stapling the ticket to the app...
Processing: /Users/example/build-mac.app
The staple and validate action worked!
Verifying that the app has been properly notarized...
./build-mac.app: valid on disk
./build-mac.app: satisfies its Designated Requirement
./build-mac.app: explicit requirement satisfied
Processing: /Users/example/build-mac.app
The validate action worked!
Finished verification.If notarization instead failed, you can determine why it failed by using xcrun notarytool log command to download the notarization logs.