

Nothing? In practice, if this were to happen on a noticeable scale it would mean Lemmy has gone mainstream. That said, within a federated system, it’s entirely possible to create isolated, defederated webrings - for example, networks consisting solely of invite-based instances. If something like this becomes a necessity, it might lead to formation of multiple such webrings and they might even decide to federate with each other someday.
For the most common scenarios I personally find CLI very easy to use: I go to the destination folder, right-click “Open in Terminal” and then type
yt-dlp linkcopypastedhere
. That’s all, multiple sites I used it with didn’t require any extra params. Maybe if you want to customize something, like make your own file naming convention, etc, GUI could be handy.