I don't know if you are using Substack on a device but I have mine on my android tablet. I also use Duck Duck Go's tracker block on the tablet that stops tracker requests. Substack is BY FAR the most intrusive app I have. Sometimes it pings my tablet over a hundred times a day. Even when it is not open. It is orders of magnatude more intrusive than the next noisiest app. I have started following Substacks on Feedly so I get the stuff but bypass the site and app.