EOA: 0x887…86E9c has never transacted before, having no send or receive transactions on any networks.
This means the address has no current owner and is not active at the moment. If the address were active, you could have contacted the owner via IDM to at least return part of the funds.
Unfortunately, this leads me to share with you what you already know by now. The funds are unrecoverable, and the Optimism team cannot help you recover them.
The case could have been different if the funds were sent to a contract address, but the funds were sent to an EOA, and only the holder of the private key to that EOA can unlock those funds.
You could contact TETHER, the company that issues USDT, but I doubt you will get any assistance from them. The best they can do is blacklist the address so that the funds can never leave once activated. But this version of USDT is a bridged token version, so I doubt it would work either way.