You could go a really long way by just giving all photographers the ability to sign their own work. If you know who took the photo, then you can make good decisions about wether to trust them or not.

Random account on a social network shares a video of a presidential candidate giving a speech? Yeah maybe don’t trust that. Look for someone else who’s covered the same speech instead, obviously any real speech is going to be covered by every major news network.

That doesn’t stop a ordinary people from sharing presidential speeches on social networks. But it would make it trivial for moderation to fact check and delete fake content.