Popups??????
What was wrong with the DM approach?
Testing one-click relay renew popup flow with nostr:npub18kzz4lkdtc5n729kvfunxuz287uvu9f64ywhjz43ra482t2y5sks0mx5sz (NIP coming). If your paid relay subscription has expired, the relay can send this popup to renew your access.
Discussion
Too much spam. People don't know what's real and what's fake. In this way, the app knows the request comes straight from the relay websocket.