Medium vs Substack vs your own website

How do you guys incorporate sites like Medium and Substack into your SEO, if at all?

Does anybody see the advantage of reposting content on either of these platforms or is it just best to keep it all on your own site?

If one were able to create an audience via Medium or Substack more readily than on their own site, would there be value to that over SEO?

Are there any best practice ways to cross-post content across these different platforms from your own website?

Thanks!