"I took the advice of Guest1053, who wrote in April, 2022 "Official site says not to use this and to only use the binary located on their website" and installed the binary from the web site. However, I found that it was unable to open ebooks - just displayed a new window with a stuck progress bar. I then installed the version from the repo via Software Manager and found, though it may be an older version, it didn't have that problem. I'm running LM21 Cinnamon. I'd be interested in hearing if others have had a similar experience."