The owner has also said via Reddit:
"My long-term vision for RedReader is to restructure the app to more easily support other sites, including Lemmy, and perhaps others such as Tild.es and Hacker News. Before the API changes were announced, I was already considering adding RSS reader functionality to the app, and I think it would be cool to work with some kind of “open forum protocol” which would allow a variety of websites and apps to interoperate with each other through a uniform API."