Not sure if you've thought about it yet but consider modifying Lemmy's source (shouldn't be too hard of a patch) to show NSFW tagged posts to logged out visitors. (And maybe force-tag all outgoing federated stuff as NSFW? Though that might be difficult for very little gain) It looks like a ghost town from the outside and that's not gonna be helpful if you want any content

Speaking of content, good luck on the moderation. You're gonna need it