I want to disable this very annoying youtube autoplay feature on my web browser. I try to disable it using youtube UI but after some time it turns on and autoplay starts working again! I am using Firefox 70 on Ubuntu. The answer from 2015 on this site doesn't seem to work for me.
I'm with you, I can't stand this feature. I don't log in to Youtube and I browse in private mode so autoplay is enabled every time I close the browser.
I wrote a userscript that checks if autoplay is enabled every 10 seconds, and disables it if so:
The usual applies: no warranty, have only tested it on Firefox with TamperMonkey (Works On My Machine™), etc.
Though if it doesn't work for you, you can open an issue on OpenUserJS and I might have time to look into it.