yes today the only way to know is using subaddresses or integrated addresses, but the client will only know about the payment if they have your viewkey, a-lá xmrchat.com
another way would be the sender publishing a zap type of note with the txid and the secret tx key which proves a payment for everyone on nostr to see, but that requires implementing a wallet in the client and sending only through that nostr app's wallet
with fcmp around the corner it will be possible to use outgoing view keys for nostr instead (timestamped explainer: https://youtu.be/prNvJWILkoI?t=957 ), or use the new CARROT addresses with a payment-validator-only viewkey tier instead of (docs: https://github.com/jeffro256/carrot/blob/a17bd68a842cca984c9e40b4bf9ea3b17176116c/carrot.md#223-payment-validator-tier )
personally for now I will focus only on tips (people can just send monero around addresses, nothing published on nostr and no viewkey or wallet integration) until the FCMP upgrade, which then will enable way more exploration