I'm pretty happy with the way I've resolved this. I publish everything to my personal blog first, then once a week I copy and paste it all into a Substack newsletter.
I get to use Substack for email distribution (which would cost me hundreds of dollars a month using most other solutions, I have 66,000 subscribers now) but my own blog stays the original point of truth.
Substack doesn't have an API for composing a newsletter, but their rich text editor DOES accept copy-pasted data - and copy-paste is the universal API.
I get to use Substack for email distribution (which would cost me hundreds of dollars a month using most other solutions, I have 66,000 subscribers now) but my own blog stays the original point of truth.
Here's the tool I use for the copy-pasting: https://tools.simonwillison.net/blog-to-newsletter
Substack doesn't have an API for composing a newsletter, but their rich text editor DOES accept copy-pasted data - and copy-paste is the universal API.