It’s unclear to me how these torrents are used. If individual books are not downloaded from them, is this only to make it possible to create similar sites in the future, in case this one is taken down?

That’s pretty cool. I might have to set it up this weekend.

What’s the use case?

I want 25 TB ☹️

My experience has been that Nextcloud can do 1000 different things, and it sucks at all of them.