Elle, I think serializing a novel is a great idea. I actually serialized my novel on Medium in 2020 before self-publishing it.

Although it is frowned upon here, I am including a link to the Medium story I wrote about the novel serializing experience and results. I plan to serialize the sequel (in progress) to the novel also.

https://medium.com/mark-starlin-writes/i-serialized-my-novel-on-medium-before-publishing-it-99878153418f

I like your Substack idea. I recently started a weekly Substack newsletter where I publish a very short humor story, a microfiction story, and a link to a longer story. Adding the serialization of my novel is something I will consider. Thanks.