Jellyfin has ebook support and allows you to download them for offline reading, which I reccommend because the ebook viewer is very basic
no, being able to move the home server of a community is different from being able to join the community from other servers. It would mean that if a server has an issue or becomes an undesirable place, the community can live on by moving somewhere else.
This sounds like a job for a raspberry pi 5 with an m.2 hat for storage, software is a less important choice here, so ubuntu’s raspberry pi flavour would be my choice. Just make sure you give it power in a form it likes.