This is one of the comment there :
Most of the complexity comes from having to deal with ReactNative dependencies during packaging. They tend to change every week dramatically which is making it difficult to write a good guide. I’m talking to Alex a lot about it and we are trying to find a way to at least give some extra guidance. Some people deployed the apps successfully and we do this as a service, but it is indeed not a very simple process.
The default background form react native haven't been answer Will Monte https://una.io/page/view-discussion?id=4304