I'm using Linux and trying to find a e-reader recently. Here is what I tested on Arch:
Calibre: Failed to open
Okular: Ugly, cannot modify margin
bookworm: No two-page view, only scrolling-mode, and scrolling-mode cannot get the reading progress
zathura: too simplify resulting in not know how to use
lector: cannot recognize epub......
Buka: cannot open the book. (I don't get the logic flow, create a list first, then import the book, then crash)
Until I found Foliate, it support two-page view w/ progress bar, it support epub will in different language (I test en_US and zh_TW), fast lookup (gtrans, Wiktionary, Wikipedia), good UI, ...etc
Fbreader is nice, I've only used Calibre for converting ebooks not sure you can read in it.
you can reader using Calibre, it's far from being a good reader
https://news-cdn.softpedia.com/images/news2/calibre-ebook-re...
If you open a .mobi in Calibre it takes tens of seconds, on a reasonably fast system, to open small (<2meg) books. I'd agree with the other comments here - Calibre is great in terms of it being powerful (web server to serve up books directly to a kindle without having to plug it in, search is ok once you know how to use it) but has a terrible UI (I shouldn't have to google to discover how to search my local library).
It will do neat things like convert to Kindle & email to the Kindle address with a button press as well so I can give access to my mum and so she can seamlessly read the epub books I have in my library on her Kindle.
It doesn't look great on the Kobo, but I can navigate pretty quickly to download a book, and I hardly ever have to touch calibre itself.
It's pretty easy to get set up running headlessly on a server somwhere.