No. I publish short stories on Medium, as well as poetry and nonfiction. If I were to publish previously-published stories or poems together in a collection, I would probably self-publish them on Amazon to avoid any copyright issues with publishers, who usually want first-publication rights.
The chapters of my novels were not published serially online or anywhere else. They were first published in 2015 by Dreamspinner press in eBook and paperback; as far as I know, there was never a hardcover edition. I pulled the first two books when they breached their contract with me in 2021, and I'm in the process of republishing them with JMS Books. Currently, the first book, Out of Order, is available as an eBook, with two more books in the series to follow. They will also eventually be made available as paperbacks POD, since JMS is a small publisher and primarily an eBook retailer.