I noticed that some of the mods here are also the mods of r/experienceddevs. That subreddit is quite active. Perhaps it would be effective to have automoderator throw a sticky on every post there, just saying welcome to r/ExperiencedDevs, please follow the rules, etc and at the bottom: Did you know we have a Lemmy community? With a link here.
r/Android has their Lemmy link in their sidebar, and they’re one of the most successful Reddit->Lemmy transitions we’ve seen so far