I know the first - it’s good.
I know the third (as: Okular) - but not as an .epub reader but as a .pdf viewer - and it works everywhere, KDE/Plasma or something else.
I rarely deal with .epub files … and they can always be converted into another format.
I don’t deal with them on my PC, except for renaming. I do, however love them on my tablet.
@OP
Best would be to install and test which one works best for you. Depending on what you want to use it for and what you need, some might work and some not.
Ok guys, thanks for all suggestions, there seems to be as many opinions as there are epub readers.
Thanks to @Mirdarthos who pointed me to the Arch list, now further down the rabbit hole.
After much consternation, I settled on Calibre. It would appear Calibre can handle any reader file I am likely to use and some I’ve never heard of.
Also Calibre handles kindle files so time to dust off my very old tablet and have a kindle reader.
Again thanks to all.
Calibre is indeed very handy; with it’s own E-Pub-Reader, and Management features. The ability to convert from one format to another with relative ease is also a plus.