Digeratimvp the AutoVideo plugin converts links to video files into an HTML5 player.
What you're probably thinking of is the MediaEmbed plugin which converts YouTube links into an iframe embedded player.
If you want to use MediaEmbed but not for YouTube, you can use the Selective MediaEmbed extension https://discuss.flarum.org/d/31404-selective-mediaembed
Having AutoVideo on or off should make no difference for YouTube links. Make sure you disable MediaEmbed in FoF Formatting if you use Selective MediaEmbed.
I'm not aware of any extension that allows uploading videos to external services, but as long as it's permitted by the terms of use and they provide an API, I don't see any technical issue. You could create an extension that uploads user-provided content to your own external account/channel, then pastes the embed link into the post. The most challenging aspect might be to setup a multi-part upload system if you want to allow large video files that won't fit in native single-request HTTP uploads. Also might need an asynchronous queue to then send the file to the end API if it cannot be ingested as fast as received.
