My team hit a less-typical situation with packaging for Mac where we wanted to include some macOS-specific features like iCloud and GameCenter that require a few extra steps in this process.
For features like iCloud communication, Mac apps need special entitlements linked to an application’s provisioning profile. To upload these apps to the Mac app store, you’ll have to not only sign the app with extra entitlements in the style of the first post in this thread, but also embed the distribution provisioning profile so the operating system knows it can trust those entitlements. I’m writing this up in case someone else finds themselves in a similar situation.
Here’s what worked for us.
**1) **Package the app as Shipping/Distribution for Mac from Unreal (we used version 4.22) as usual.
NOTE: make sure you uncheck “Include Debug Files” in your project settings. If you package an app with a debug .dSYM file in it, Application Loader will fail with the cryptic ERROR ITMS-90135: "The executable could not be re-signed for submission to the App Store. The app may have been built or signed with non-compliant or pre-release tools.” and you’ll lose an entire weekend figuring out what the heck is going wrong 
2) Edit the plist of the exported app. You can either open it up via the terminal at [FONT=courier new]MyGame.app/Content/Info.plist or navigate there via finder (Show Package Contents) and double-click it to open it in xcode.
You’ll want to set the Application Type, version strings, and possibly the bundle id to match the identifier you’re uploading to.
3) Remove the file [FONT=courier new]MyGame.app/Contents/Resources/RadioEffectUnit.component and the directory [FONT=courier new]MyGame.app/Contents/UE4/Engine/Build. As mentioned earlier, the RadioEffectUnit stuff can cause problems with packaging. As far as I can tell it’s safe to kill it, but if you actually need these files for your game I’m not sure what you should do 
4) As of 2018, the Mac App Store will not accept applications with 32-bit code. Your exported Unreal 4.XX game should be good to go, but a few of the third party libraries in your package include 32-bit and 64-bit code. We have to remove it. In our case we did that with:
lipo MyGame.app/Contents/UE4/Engine/Binaries/ThirdParty/Ogg/Mac/libogg.dylib -remove i386 -output MyGame.app/Contents/UE4/Engine/Binaries/ThirdParty/Ogg/Mac/libogg.dylib
lipo MyGame.app/Contents/UE4/Engine/Binaries/ThirdParty/Vorbis/Mac/libvorbis.dylib -remove i386 -output MyGame.app/Contents/UE4/Engine/Binaries/ThirdParty/Vorbis/Mac/libvorbis.dylib
Though it’s possible your exported package might have other libraries that need stripping.
5) Now add in your Mac App Store Distribution provisioning profile. You may have to create this in the developer portal and download it. Rename it “embedded.provisionprofile” and move it to [FONT=courier new]MyGame.app/Contents/embedded.provisionprofile
**6) **Now prep your entitlements xml for signing. This will vary based on what entitlements you need. Create and fill in a temporary “mygame.entitlements” file (you can name this whatever you want; it isn’t going in your application). Ours looked something like:
<?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>com.apple.developer.icloud-container-environment</key>
<string>Production</string>
<key>com.apple.developer.icloud-services</key>
<array>
<string>CloudKit</string>
</array>
<key>com.apple.developer.icloud-container-identifiers</key>
<array>
<string>iCloud.com.mycompany.mygame</string>
</array>
<key>com.apple.developer.game-center</key>
<true/>
<key>com.apple.security.app-sandbox</key>
<true/>
</dict>
</plist>
7) It’s signing time. You’ll have to sign the game binary, all dynamic libraries, and finally the .app itself. We did this with:
codesign -f -v -s "3rd Party Mac Developer Application:" --entitlements mygame.entitlements MyGame.app/Contents/MacOS/MyGame
This command signs all .dylibs in the file. I’m not sure you need entitlements here.
find MyGame.app/Contents/ | grep .dylib | xargs codesign -f -v -s "3rd Party Mac Developer Application:" --entitlements mygame.entitlements
Then sign the whole app:
codesign -f -v -s "3rd Party Mac Developer Application:" --entitlements mygame.entitlements MyGame.app/
**8) **Finally, build the .pkg:
productbuild --component MyGame.app/ /Applications --sign "3rd Party Mac Developer Installer:" MyGame.pkg
And upload with the Application Loader. If you have any issues with your icon settings or other plist information, those warnings will appear here. Redo all of step 7 if you make any changes to your MyGame.app folder.
Feel free to reach out if you hit any issues trying this. Caveat emptor, we just got this working today and haven’t verified that the uploaded package works once installed by users.