LobsterDAO
This uses a modified MerkleDistributor, which allows to issue a lazy airdrop using temporary IDs.
In this example it uses Telegram chat_id to allocate to active users in a certain chat.
A user needs to provide a merkle proof of (index, amount), as well as a signature of (index, account).
A signer account verifies the address provided by a user and discards the temp ID. This way it stays private if the full merkle tree is never publicized.