You don't need to work with free provisioning profiles manually.
Automatic signing possible from unreal editor without creating that dummy blank xcode project with same App ID.
Connect your device to mac.
Create new mobile project in unreal editor , then in project settings for IOS change the field with Bundle Identifier to com.yourcompany.[PROJECT_NAME] (don't change the macro [PROJECT_NAME] , leave it as is).
Do not choose or import any provisions and certificates.
Then check the Automatic Signing chekbox and fill the IOS Team ID field (value for this field can be examined in any of your xcode project signed before with your free dev account - right click on .xcodeproj file, then choose Show Package Content, then view content of file project.pbxproj and find DEVELOPMENT_TEAM = ??????????; take this value)
Select fro menu File--Package Project--IOS and wait while buildng .ipa file.
Drop builded .ipa file to your device in Xcode's Devices and Simulators window.
I've tested all this steps right now and it works with my free dev account.