Found this article on platformer.news - who have left Substack for Ghost.
Extremely sharp observations on where Substack got it wrong.
TL;DR
And in one key respect, Substack is even more vulnerable to this criticism than social networks had been. Extremists on Facebook, Twitter, and YouTube for the most part had been posting for clout: those platforms made it difficult or even impossible for them to monetize their audiences.
On Substack, on the other hand, extremists can post for money. The pieces are now all in place for an extremist Substack to grow an audience using the platform’s recommendation systems, and monetize that audience via subscriptions. And Substack, as it does with all publications, will get 10 percent of the revenue.