Strategy Inc. (MSTR) (formerly MicroStrategy) holds massive amounts of Bitcoin, causing its stock to trade as a high-leverage proxy for Bitcoin's price.

If you want to own the digital assets themselves (e.g., Bitcoin or Ethereum), you must use a crypto exchange or a multi-asset brokerage. What is Cryptocurrency and How Does it Work? - Kaspersky

Companies like Coinbase (COIN) allow you to invest in the infrastructure of the market rather than a specific coin.