Today, Optimism bridge is taking almost all ETH derivates to be withdraw on Mainnet with the challenge period.
Here’s the current list available : ETH, wstETH, rETH, cbETH, frxETH, rfwstETH.
The Bridge already accept sETH from Mainnet to Optimism but there’s currently no way to bridge sETH to Mainnet for the return, also there’s none third party Bridge (even Synthetix Bridge).
sETH is increasingly used and could be added to the list.
Bridge token list : Ethereum token lists
sETH (Mainnet contract) : 0x5e74C9036fb86BD7eCdcb084a0673EFc32eA31cb
sETH (Optimism contract) : 0xE405de8F52ba7559f9df3C368500B6E6ae6Cee49