Internal use only
To better support some of our open source efforts, we are publishing this @office-iss/react-native-win32 JS package that office uses on win32. This is not a package that is generally consumable by other since it requires Office's UI framework which isn't open source. But it does allow some of our other cross platform efforts to be able to open source their work where previously its been unable to if Office win32 was one of the target platforms. This will enable projects such as our cross platform component libraries to be able to be published to open source.
We do have a solution for running react-native in a win32 app. You can run react-native-windows on win32 using Xaml Islands. We are working on expanding the set of supported Windows versions to broaden the support of that, and provide more samples of how to do that.