jirafey/yt-invidious

How to install:

1. Be on Developer/Nightly Firefox Edition
2. Go to about:config
3. Make sure: xpinstall.signatures.required is set to false
4. Go to extensions -> Manage extensions -> Click on the settings gear icon

5. Download the yt-ind.xpi file
6. Install Add-On from File...
7. Choose the yt-ind.xpi file

8. And voilà, it's installed.