Peruse
Peruse is a free multi-platform open source software for reading books and comics from KDE
Calibre
posted in: E-book, E-book converters, E-book editors, E-book managers, E-book readers, Office, Software | 0
Calibre is a free, open source cross-platform software for reading, converting, and organizing e-book collections
OpenComic
OpenComic – free and open source cross platform program for reading comics and manga
Komikku
Komikku – online/offline manga reader for GNOME, developed with the aim of being used with the Librem 5 phone