You can't plug it into your computer and drag files onto it?
(I actually don't know if side-loaded KFX actually support notetaking on the Scribe)
At least then it doesn't require uploading to Amazon's servers.
So far, I haven't seen any evidence that the readers or apps will be getting native ePub capabilities.
Even then, ePubs sent to your own account still are treated as second-class books. Most importantly, they are not rendered in the "enhanced typesetting" engine, while Amazon-bought books (often likely from the same source ePub) do get that.
It's really hard to interpret this as anything other than making it intentionally hard/annoying to import DRM-free purchases from third-party bookstores.