Stripe shares most transaction details with customers like Substack. Pretty much everything except full address and full card number, for example:
Now, will Substack share this information with Substack publications? Maybe, I don’t know how exactly Substack works, but many similar platforms will have a publisher link their own Stripe account to accept payments, and then the publisher would be able to see this data.
For example, GitHub Sponsors works this way, so a person you sponsor on GitHub would receive this data.