Yes, you can lock through stake Dao and yearn without curve.fi. Stake Dao is a platform that allows users to stake their assets and earn rewards. Yearn is a platform that allows users to earn yield on their digital assets. Both of these platforms allow users to lock their assets in order to earn rewards, but they do not use Curve.fi to do so. Curve.fi is a decentralized finance protocol that allows users to trade assets across different blockchains. It is not necessary to use Curve.fi in order to lock assets in either Stake Dao or Yearn.
