This isn’t new news as such, but people keep being surprised by it, so it’s worth repeating. Substack hosts, profits from, and promotes explicitly Nazi content, and if you are adding value to that network, you are helping them to do so. 
the Guardian
Revealed: How Substack makes money from hosting Nazi newsletters
Exclusive: Site takes a cut of subscriptions to content that promotes far-right ideology, white supremacy and antisemitism