Substack is just a place to post writing and let people subscribe for money so it can be used to post chapters of fiction just as well as an article. I only know of one person who was posting a novel on there, and not sure if they were making a lot of money from it.

There's also tons of subreddits like r/WritingPrompts to practice or r/NoSleep to post short horror fiction. There are huge audiences on both of those. A post from NoSleep is getting made into a Steven Speilberg movie: https://variety.com/2019/film/news/spire-in-the-woods-steven...

RoyalRoad is huge though. Here's the top story from it: https://www.royalroad.com/fiction/21220/mother-of-learning authors usually get a following on RoyalRoad and then they can start a Patreon where people who donate get early chapters. Other authors go the Kindle Unlimited route where they self publish their novel on Kindle Unlimited after they've got a fanbase and plenty of people make a decent living from it.

This is all the modern version of how older authors got started: by submitting short stories to be published in anthology magazines. You have to love writing and be willing to do it for a long time before you pop off though. The way he was describing it didn't resemble that to me.