The Developer subscription plan does not let you build and/or upload packages that are ready for publishing to the Apple App Store or Google Play with AppBuilder.
A publishable package is a package signed with an App Store provisioning profile and certificate or with a Google Play self-signed identity. You cannot submit a package signed with an Ad Hoc, an in-house distribution, or a development provisioning profile to the Apple App Store.
You can, however, produce a build that is publishable to the Windows Phone Store and a build that is publishable to Telerik AppManager (which lets you handle your own private app store for Android or iOS apps). You will need to manually upload such builds to the corresponding service. You can read more about Telerik AppManager here
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