Substack is a fine place to write. It is also a company, with a payment processor, a hosting provider, an app store listing, and a legal department. Each of those is a place where someone else can decide your writing should stop appearing. Most writers will never hit that wall. The ones who do get no warning.
Parler is the clearest example. In January 2021 it lost its app store listings, then its hosting, in the space of two days. The service had done nothing new that week. What changed was the willingness of three companies to keep it reachable. Anyone whose only copy of their work lived there watched it go dark.
Notice what got cracked down on. Not the existence of the posts, which sat on disks the whole time, but the means of finding them: the app, the domain, the servers with public addresses. Discovery is the fragile part. Permanence is cheap if you plan for it.
Keep is that plan. It is a small writing network that runs on Urbit, a personal server system where every participant owns a cryptographic identity and runs their own node. We run the node for you. It mirrors your Substack as you publish, keeps a copy of your subscriber list, and lets readers follow you directly. If the day comes when the front door closes, the back door is already open, and it is yours.
Think of it as insurance. You pay a little attention now, and you hope never to need it.