chrome://flags also has an autoplay setting that requires user interaction before playing media
Even the strongest setting "Document user activation is required" isn't good enough. It means one click in the page will cause the video to start playing, which is annoying and highly game-able. I don't want a click somewhere on the page to cause a video elsewhere on the page to start playing. Every content site is going to do something to require you to click, like not showing the whole article and having "Click to expand".
I've been using AutoplayStopper and it works wonderfully: https://chrome.google.com/webstore/detail/autoplaystopper/ej...
Once you start using it it's shocking how many (attempted) autoplay videos there are that you never noticed.
That's why it is so refreshing to see at least one of them (Firefox) actually trying to get it right.
The technical term for a browser is "User Agent". That naming may be historic and old-fashioned, but it was named that way for a reason. It's time to restore the original meaning, to make the browser an agent who actually acts on behalf of and in the interests of the user, not the website creator.