https://fbreader.org/
Favourite Book Reader – FBReader
An ePub reader supporting Readium LCP DRM. Also opens fb2 and other formats. Free, fast, configurable. Network book sources, custom OPDS, cloud sync.
favouritebookreader
https://snapcraft.io/fbreader
Install FBReader 2.1 on Linux | Snap Store
Get the latest version of FBReader 2.1 for Linux - Your Favourite eBook Reader
2 1snap storeinstallfbreaderlinux