Greasy Fork is available in English.
Shows empty navigator.plugins and navigator.mimeTypes collections to selected websites
Some sites prefer to use Flash but work perfectly well (or better) if Flash is not installed.
To apply this to the site of your choice: You can add the site's address to the user included sites for this script to blind them to your plugins. See screenshot below.
To test how this script should work: You can compare these pages:
https://www.jeffersonscher.com/res/plugins.html -- not blinded, sees all plugins
http://www.jeffersonscher.com/res/plugins.html -- script hides all plugins from the page
Inspired by this thread: https://support.mozilla.org/questions/1115681
