In a way this is the opposite of what you're asking, but this is kind of the reason I set up https://lemmit.online - To allow people to get quality content like !itookapicture@lemmit.online automatically onto Lemmy.

Anyone can request subs to be synced, and admittedly, not all of those requests make sense, since it doesn't sync comments. But the goal is to bootstrap content creation / combat people returning to reddit because they miss content there.