If you've got a free Substack publication, you can start from anywhere. If you're planning to add paid subscriptions, you can view a list of countries supported by Stripe, our payments provider.
India is an exception to this list for additional technical reasons. Our paid subscriptions are currently in beta for India. During this time, India-based writers can still add paid subscriptions, but Substack does not currently charge a fee (you will still be charged a fee by our payment processor). Please note that Substack's 10% fee will eventually apply once India-based paid subscriptions are out of beta, and plan accordingly. (Note that this information does not apply to India-based customers of your publication, but to India-based writers who would like to set up paid subscriptions.)