Any advice for a large subreddit's (19 million subscribers) new lemmy instance?

I'm one of the r/futurology admins, and involved in setting up our new Lemmy instance - https://futurology.today

While we don't want to spam our user base, we'd still like the site to do well and promote it. We've 19 million subscribers, and by far the most traffic we get is the top posts that get on people's front page or r/all. We've sometimes used stickied comments in these posts, but I'm wary of doing that, as many users might perceive it as spam.

Any advice for promoting our site, bearing in mind 95%+ of eyeballs go to these top posts.?

Here's our onboarding announcement.

https://www.reddit.com/r/Futurology/comments/15wi75l/rfuturology_is_now_in_the_fediverse_at/