Here's an example of an OPA event posted to Nostr.

https://plektos.app/event/naddr1qvzqqqrukvpzqejwqu87yhnkmh8054yjnsx7gtk26zqspy6s0cjdu33zqagumda2qqvrvwphv93rxdeevdjnxd3cvvenjcf3xyekzdfexg7uqg3s

nostr:note1y42yg8959nc360c587zqf0pdd6ywsvgh03ua4rqfw8yltef6prksgcatz9