Maybe you found your niche on substack, and that would be great. Fingers crossed for the growth of your newseltter. :D

(edit your comment and add a link to it by the way :D)

I agree with the mailing list, it's good to have in case of platform change. (And it's good that Medium gives the possibility.)

I agree with multiplatforming at one point; when the writer has sufficient experience and content (as David said in a comment here).

But at the beginning I still recommend focusing on the craft and one platform. If the platform goes down, then it's always possible to change (and bring your mailing list with you).