Just add a button on the Substack Dashboard and use this link

https://zapper.fun/zap?id=npub1tjjvjppc7efxtdgxyss6lrpfryglpe3nezszqj276txdfmm6gt9qms44cz

It's one of the coolest nostr projects that doesn't get a lot of recognition.

https://github.com/nostrband/zapper