Random Invidious Video by jeff

Currently, this looks for the website "www.invidio.us" to be the site visited. When you're on your subscriptions page, a small icon will appear on the address bar, which you can click to open a random video.

I recommend changing your Invidio.us settings to include 100 or 200 videos, so that it chooses more randomly. I also recommend changing your settings to show only the latest video from each channel, so that channels that spam don't get chosen more often for random viewing. But it's up to you!