Deep Tide TechFlow News, August 29, according to official documents, 21Shares has submitted an S-1 filing to the U.S. Securities and Exchange Commission to launch the 21Shares Sei ETF, which aims to track the price of SEI tokens. This ETF will not use leverage or derivatives; SEI is custodied by Coinbase Custody, and shares are expected to be listed on the exchange, with authorized participants able to subscribe and redeem using cash or physical assets.