Yes, the Eth Vault does use Lido stETH. Lido stETH is a tokenized version of ETH that is held in a secure multi-signature smart contract and is designed to provide users with a secure and easy way to access Ethereum-based DeFi protocols. The Eth Vault allows users to securely store their stETH tokens and earn rewards from yield farming and other DeFi protocols. By using Lido stETH, users can reduce their risk of losing their funds due to security issues or other factors, while still being able to take advantage of the high yields offered by DeFi protocols.