beacon.validator.indextable gives an index of Beacon Chain validator index, pubkey, withdrawal credentials and withdrawal address of each validator.
This table updates daily with newly activated validators.
Finding the total number of validators that have withdrawal address to Lido Withdrawal Vaults
count(distinct validator_index) as validators
where withdrawal_address = '0xb9d7934878b5fb9610b3fe8a5e441e8fad7e293f' -- Lido Withdrawal Vault
group by 1