oh wow! I didn't realize the 100 follower thing was a "new" thing. Yes, it is very tricky to get followers on just a typical blog.
For me, I think I picked a topic that happens to be trending. The entire world is focusing in on blockchain. I wonder if your experience in cybersecurity could give you and 'edge' in addressing that subject, but only if you wanted your blog to do that.
Otherwise, yes, it can be very difficult. I know that in the short time I have been writing, that in my top month, January, I had written 23 articles. It seems that Medium rewards for recent articles, full reads - so 5-7 minute "read" times was optimal, and engagement - views, claps, and comments.
One thing that helped me get a few more followers was I would look on Twitter to see other people with larger followings and find one that was relevant to one of my articles. Then I would post my article in that Twitter post. I would put some kind of caption that would relate MY article to what the Tweet was about. Then, anyone that reads their post might have a chance to see what my article was about.
I would do that in as many Tweets as I could find, but I would be careful not to spam the tweet, otherwise they would just block me.
Thank you for sharing - I definitely learned something new!