I liked this article (though I didn't read it fully yet):
https://medium.com/libraries-io/what-does-a-sustainable-open-source-project-look-like-bf9b8cf824f8
I got it through the people at opencollective.com; the ones who got me
to create #14743: "Get money from ads on our website or code" :)
I want to continue reading it to feel good about the parts that we're
doing well already and also get inspiration from the parts that we might
be still lacking.