Until SDK 7.5.X one could open the Xcode project from a device build (-T device) and simply run it via Xcode. This was very useful for easy native debugging of both the SDK core and natives modules.
Since SDK 8.0.0 this is now failing due to the core-js polyfills which are added to the app outside of our usual JS processing and thus are not part of the encrypted JS assets.
Apart from the issue mentioned in this tickets this may also have a negative performance impact since i would assume loading the polyfills from the encrypted assets is probably faster then loading them all from file.
EDIT: With latest master the issues with polyfills were resolved. Only the _index_.json used to resolve require paths is still required.
As a workaround the following build phase can be added to the Xcode project which copies the required files into the app bundle: