@Matt Eaton thank you for your prompt response. We were a bit inspired by the remark from pascalrs :
After adding it to our App ID in the developer portal and adding it to the entitlements.plist manually, Xcode was kind enough to automatically generate the new provisioning profile.
So In Xcode Project we did select the project and the iOS target. At the
Signing & Capabilities tab, we have the
Signing (Debug) section, where we disabled
Automatically manage signing and added the development provisioning profile according to the
instructions from Quinn.
Below this is the section
Signing (Release and Ad Hoc Distribution), which is still set to
Automatically manage signing.
The
Xcode Managed Profile has a small info button. When clicking it, the second row showed that it was updated today.
Scrolling down to the
Entitlements section, shows that
com.apple.developer.networking.multicast is added.
In order to validate this, we archived the Build. We submitted it to App Store via Xcode. While using automatic signing, the overview showed that the entitlement was included.
After deleting the app from an iPhone with iOS 14.2, we installed it from TestFlight. It works flawless with UDP discovery for DLNA devices:
The system alert with Local Network access permission was shown at the correct timing.
Accepting it would instantly report responding DLNA certified devices
These devices could be controlled, similarly as compiled with Xcode 11 and running on iOS 13.
The Local Network access toggle is shown in iOS System settings -> App Name
Uninstalling the app and launching it, will trigger the system alert with Local Network access permission again.
Based on this TestFlight observations, do you expect that a Distribution Provisioning Profile is required, or can we safely rely that the Xcode Managed Profile has been correctly updated automatically (automagically)?