Is it suitable to ask questions about Ebooks copyrights, legitimacy of hosting ebook torrent files, magnet links; or hosting ebook webpages with covers and metadata on Ebooks StackExchange?
My inclination would be to say no; those are questions about law, rather than about ebooks, and would be better suited to a site like https://law.stackexchange.com/
Copyright is a very specialized type of law. I am not convinced that it would be wise to leave it to the law site https://law.stackexchange.com/, where discussion can probably become far too technical (legally technical).
However copyright issues are addressed in the writers site https://writers.stackexchange.com/ , and it would be unreasonable to duplicate that here, unless there are issues that are specifically relevant to e-books (though even that is likely to be addressed in the writers site). I actually know of some such issues.
However, it may be convenient to have a few simple copyright questions answered here in a general way, if only to tell users where the should rather look for such questions.
Also answering here questions that were not answered on the other sites may also be ok. There are many sites with intersecting areas of interest, and questions get answered in whichever site gets the question first.
My feeling is that copyright questions for ebooks are important to publishing and that the other two SE don't adequately address ebook-specific issues.
First the writer site may not address digital issues very well. Second, the law site https://law.stackexchange.com/questions/tagged/fair-use has some fair-use questions (for example), but they are so broad that you would not get many replies specific to the publishing industry.
As long as questioners understand that lawyers are not on this SE and that answers shouldn't be considered legal advice, I don't see why copyright questions should be excluded here.