Well, I duplicate most of what I do here on Substack as a matter of course (no sense having one's eggs all in one basket) but I also put exclusive bits and pieces here and exclusive bits and pieces on Substack (I'm serialising my supernatural mystery thriller novel The Thistlewood Curse on Substack at present, for instance).
I've seen many Medium ups and downs over the years. I've no idea how they operate. I just write here. All I know is the issues are a bit Karma Chameleon, to be honest (they come and go). So I'm afraid I can't really offer an opinion beyond a vaguely optimistic I daresay it will sort itself out.