Actually this is a large amount of money that you can use to invest in many good tokens. You can invest in bitcoin if you want because it is the only token from which profit is easy and safe. Also eth, bnb, doge are many good altcoins that you can buy before the bullish market comes. But it is better to do an independent analysis because you have to make your own decision whatever the results of your own analysis. So here only you can get different opinion but right decision should be based on you.
eth, bnb and dogecoin are the three altcoins that of course will continue to have the potential to continue to have good value, and currently solana is also following that (if I had $20k then I would also include solana on the list)
however, still use the bitcoin investment concept of 50-70% of the total money while the rest is altcoin