Apple restricts playing keynote videos on Linux. I have found various solutions for using VLC and Apple keynote links but I really like this simple one explained below.
Open Chrome (install if you are not using it) and load apple.com on your browser. Then you must change UserAgent string to use the UserAgent string of Firefox on Windows so Chrome will pretend it’s Firefox running on Windows.
To change UserAgent of Chrome, open Menu > Tools > Developer Tools. Click on the Gear icon at the bottom-right corner and select UserAgent checkbox. Choose Firefox for Windows.
Thats it. Now the video will be loaded in your browser (I’m using Ubuntu so the QuickTime plugin is installed by default). If the online player is stucking, right click on the video and play it with the movie player.