Caveat lector: I wrote this post in high school; it’s likely outdated and poorly written.

Installing flash player 10 in Ubuntu does not install it for Liferea.

The fix for this is very simple:

  1. First install Flash Player 10 using this Tutorial

  2. Next execute this command in the terminal:

     sudo ln -s /usr/lib/firefox-addons/plugins/libflashplayer.so \
                /usr/lib/xulrunner-addons/plugins/libflashplayer.so
    

Flash Player 10 should now work in Liferea.