Solana, Cardano and other crypto assets have a slim chance of being approved as spot exchange-traded funds (ETFs) in the United States and could have an even more difficult time attracting investors. Speaking to Cointelegraph, Katalin Tischhauser, head of investment research at Sygnum Bank, joined a recent string of commentators who expressed skepticism that other altcoins can follow Ether (ETH) and Bitcoin (BTC) as spot crypto ETFs in the United States. Tischhauser said the main obstacle to approving other crypto ETFs in the US is the lack of trading venues that the Securities and Exchange Co…