Maybe you can always check Coinmarketcap to see many exchanges you can use to trade future and try your luck.
We have good exchanges like Binance, Bybit, Kucoin, OKX etc that can enable you to trade with less tax and free.
Please make sure you do the necessary research because most of these exchanges are limited in some regions so it's good you try and know where they are limited so you don't get restricted later after you fund your account. There are centralized exchanges.
He can use Coinmarketcap but I will prefer Coingecko which has been listed up because Binance has already bought Coinmarketcap years ago and he will use that to favour itself as the best exchanges and superior to other exchanges but which is not true. There are many other exchanges just like the ones that you mentioned like Bybit and OKX.