3 years ago I started a newsletter about robotics (https://weeklyrobotics.com/) and about month ago I opened it to advertisers and started earning about $600 a month from ads.
I’ve occasionally posted some issues on hn and /r/robotics. Every week I share the issues on Twitter, Facebook and LinkedIn. From these LinkedIn seems to have brought the most interactions so far.
On a couple of occasions I traded shout outs with some newsletters and I think this was the most effective method for obtaining new subscribers.
