Just want to make sure, do you have ETH on Optimism as a visible asset in your Brave Wallet?
For example, screenshot from mine. You see where ETH on Optimism has a checkmark in the box, so it’s visible. If yours is off, then you wouldn’t be seeing it.
If you need a bit of help on how to check all of that, you can kind of see it at * Adding new asset to Brave Wallet