The U.S. Securities and Exchange Commission (SEC) has acknowledged Grayscale’s filing for a Solana-based exchange-traded fund (ETF).This is the first time the SEC has engaged with an ETF proposal tracking a cryptocurrency that was once considered a security.The SEC's acknowledgment is seen as a positive sign for crypto firms, indicating a possible shift in crypto regulation.The regulator now has a 240-day window to approve or deny the proposal for the Grayscale Solana ETF.