Since you are on Coinbase, you might try steem-engine.net. There you can trade into BTC or LTC and send that to Coinbase.

Bittrex also lists Steem. You might (probably will) get a better price over there, but I'm not sure if they are accepting deposits right now.

Also, you may have missed the whole blockchain split. In Spring of 2020, a new chain was created, called Hive,; all wallet balances at that point were duplicated on the new chain. You should have the same account name/keys over on Hive. Use hive-engine.com or Bittrex for those coins as well.