Having a trading account in Bittrex makes him a customer,not a trader or businessman.
There are narrow conditions where traders may be considered by the IRS to be engaged in a business, but that only applies to those trading securities (not cryptocurrency like Bitcoin), and trading activity must substantial, continuous and regular. None of that is indicated by the OP. For more info on these conditions, see here.
Most traders -- even day traders -- are considered "investors" by the IRS. Their capital gains are considered unearned income, not business income.
I learned yesterday Bittrex International is located in Malta and you will be redirected automatically to Bittrex International when you are not in the US.
No US no IRS. Laws of Malta have to be considered.
Same Story for Binance. It's also in Malta since 2018