For anyone who needs to know...
You can right now earn $30 worth of Optimism rewards on Coinbase learning.
The quests involve, downloading the Coinbase Wallet, transferring some Ethereum (on OP network) to the wallet, minting a free NFT, making a swap, staking in defi (you have to leave this staked for 7 days).
On all quests you are given clear and easy to follow instructions.
You will spend around $5 of Ethereum on gas, so you should come out with around $25 overall for nothing.
Enjoy.
