What’s really weird about Substack is that you seemingly can’t subscribe to a newsletter and read it in the app without getting every post emailed too. I just want to read in the app.
fwiw, part of their schtick was newsletters and that you, effectively, never had to open their app. Seems like they designed for one and not the other. That said, during launch day they took a lot of feedback from here so they might hear you if you reach out.