I just skip Medium due to the walled garden. Even worse than Reddit. I have never come across a link to substack... are they an even higher wall that search engines are stymied by?
I fail to get why you think putting your stuff on Medium is a good idea.
I'm liking Medium less lately because of the number of pop-ups. I have to close three, maybe two sometimes, to get to the content.
I get the appeal of visibility, but I'd still suggest trying a WriteFreely instance; you'll get (and support) federation, and you can still self-promote on Lemmy and Mastodon - I've yet to see any real push-back on self-promotion, unless it's a controversial position, such as taking a strong stance on a divisive topic and acting as if you're an authority when you aren't. And even then, the push-back is the same whether or not it was self-promoted.
I never come across Medium articles unless someone creates a Lemmy or Mastodon post linking to it, anyway, so I'm guess you're expecting higher visibility on the Facebook/X platforms?