In most countries receiving a payment for posting would be taxed, if you then convert it to another form of currency, say Bitcoin to USDT or whatever, then you wouldn't be paying tax again for that conversion since your cost basis is basically the same as the price. So, in reality, in terms of tax it doesn't matter if you use the same coin you received or you convert it to something else, the tax is basically the same.
It's true you will not be taxed for converting USDT to BTC or vice versa, but if you sold your BTC or any other altcoins higher than what you win from gambling, you will need to pay capital gains.
Let's say you convert $5,000 to BTC, you will get 0.074 BTC.
In sports you're betting in USD, not in BTC, so you will see $5,000 in your account, you stake all of your money on football match where the odds is @2.00.
Turns out you win, which mean your money now $10K or 0.148 BTC.
You choose to withdraw your coins to exchange or wallet, then you wait until bull season.
Bitcoin price up, your 0.148 BTC now worth $20K.
If you sell all of your coins, you need to pay both taxes, $5K is the profit from gambling and $10K is the profit from capital gains.