Reading/writing multimedia files (videos, pictures, audio, text documents...) on an NTFS partition works without issues. The issue arises when using one as a system partition (to install video games on, or worse, the whole Linux install). I don't know exactly what's causing issues, but my guess is metadata/permissions get messed up on NTFS when used on Linux.
You should also ask yourself what kind of books you want to read. Black and white comic books, for instance, can be read on an e-reader, as long as the screen is big enough.
It was always a tankie den. The Lemmy developers are very openly tankies.
They held their heads relatively low during the whole Reddit exodus, but that's about it.
Reddit is required by EU law to delete all of your data if you ask them to (and you're an EU citizen). I suspect it's much harder to do on the fediverse, though in theory they're subjected to the same law.
For your links (I believe it works with files too), check out Heimdall. It's not offline, but it's FOSS and selfhosted.