Coinbase allow you to buy ltc, eth, bch and btc. If you wanted to buy monero you would first have to buy one of those then transfer to another exchange.
Edit: my bad. I got confused by the new Robinhood ux:
Anyone that uses the Robinhood platform to buy Bitcoin or Ethereum today comes into a market that has lost roughly half of its value over the past couple of months.
I believe those coins can be tracked but not bought.
Better source:
https://support.robinhood.com/hc/en-us/articles/360000088623...
Starting in February, Robinhood Crypto supports buying, selling and real-time market data for:
Bitcoin (BTC)
Ethereum (ETH)
Robinhood Crypto also supports real-time market data for the following:
Bitcoin Cash (BCH)
Bitcoin Gold (BTG)
Dash (DASH)
Dogecoin (DOGE)
Ethereum Classic (ETC)
Lisk (LSK)
Litecoin (LTC)
Monero (XMR)
NEO (NEO)
OmiseGO (OMG)
Qtum (QTUM)
Ripple (XRP)
Stellar (XLM)
Zcash (ZEC)
So not really the game changer you are saying it might be.