I want to open PDFs from Calibre in Okular. I found a thread https://www.mobileread.com/forums/showthread.php?t=102237 it says Calibre opens these files in whichever app it's configured in the OS
I added an entry to .config/mimeapps.list
[Default Applications]
x-scheme-handler/http=firefox.desktop
x-scheme-handler/https=firefox.desktop
x-scheme-handler/chrome=firefox.desktop
text/html=firefox.desktop
application/x-extension-htm=firefox.desktop
application/x-extension-html=firefox.desktop
application/x-extension-shtml=firefox.desktop
application/xhtml+xml=firefox.desktop
application/x-extension-xhtml=firefox.desktop
application/x-extension-xht=firefox.desktop
x-scheme-handler/about=google-chrome.desktop
x-scheme-handler/unknown=google-chrome.desktop
x-scheme-handler/lens=OpenLens.desktop
[Added Associations]
x-scheme-handler/http=firefox.desktop;
x-scheme-handler/https=firefox.desktop;
text/html=firefox.desktop;
application/pdf=org.kde.okular.desktop; <--------------------------
Restarted Calibre, it still opens PDFs in Firefox
How to use external ebook viewer (Okular) Calibre