IMO don't use Medium as its tough for content exploration as a user.
I think the best option is to setup a static site generator using whatever tool works for you - ideally a tool that allows your users to search for blog posts, and filter posts by tags.
I would probably start with Wordpress to quickly get started, and explore other options as needs arise.
I'd setup a static site with something like Hugo , but if you don't want to waste too much time Medium or equivalents is perfectly fine.
- Dont use Medium, they will paywall your users and you cant use your own domain
- Dont roll your own, it will waste time and marketing will get mad.
- Not sure about substack tbh so
My honest recommendation is to use Ghost, it has the highest quality themes and CMS (when compared to wordpress) and you can self host if you'd like or let someone else take care of the mess for a small fee.
Just spin up a Wordpress site and call it a day.