UPDATE: I was mistaken about the need for a Mitra instance/account to be able to support. In silverpill's own words: "I'd like to clarify that subscribers are not required to have Mitra account. Yes, people need to navigate to the payment page that is located on the subscribee's server in order to subscribe, but they don't need to create an account there. After subscribing you can read subscribers-only posts from your main Fediverse account, as long as it has $ETH profile metadata field with your payment address (the posts should be displayed as direct messages by Pleroma/Mastodon)."
https://mitra.social/objects/0182e4e3-5afb-82ee-af21-61c6040567e2