How do I go about it with an ETH address? Is that also sufficient? Can I just use MyEtherWallet and create a message similar to the one Theymos asks for when it comes to proving ownership for BTC addresses?
Unfortunately for OP (and ss far as I know) signing ETH address is not accepted method of proving the account ownership, and only signed BTC address is accepted, as mentioned by theymos in
Recovering hacked/lost accounts . If ETH address is accepted it would be mentioned there.
Looks like that there are some issues with that, as explained by @pooya87
it is not just about this being a "Bitcoin forum", the problem is the lack of a trusted wallet to do the signing and verifying of signatures and also whether the person verifying has that wallet installed. otherwise the processes are the same. bitcoin uses secp256k1 curve while ethereum uses secp256r1 curve with only different constants but same size signature and same EC calculations.