I tried following the A Beginners’s Guide to the WordPress REST API tutorial
It didn't work for my own (free) WordPress account, but when I used the "the-art-of-autism.com" (a premium account on which I have admin privileges) in place of "yourdomain.com" I was able to follow the tutorial successfully.
However, none of the Routes or Endpoints seem to give me what I want, which is the number of followers for an arbitrary WordPress account on which I don't have admin privileges. I'm encouraged by the REST API Handbook Reference page stating "The REST API provides public data accessible to any client anonymously, as well as private data only available after authentication."
I can't find any way to determine the number of followers, or what public data is accessible anonymously. Can you help with either of those? Thanks.