https://github.com/sandwichfarm/nostr-watch/issues/678#issuecomment-2294807863

There has been tall about putting "accepted kinds" into NIP-11, which would be the first step to making these relays discoverable if I understand the problem correctly.

Updated answer: NIP-22 via NIP-66

https://github.com/nostr-protocol/nips/blob/42c510183434809b729557d25c403cfe2ca1e7fa/66.md#single-letter-tags-indexed

See `k` tag in `30166` event.