what’s the best way to covert btc to usdt and usdt to btc?

i got 100$ worth of btc on bitcoin chain , what's the easiest way to covert it to usdt or usdc on alt chain and get it on trustwallet and vice versa?

looking for decentralised way , cex are easiest way but unfortunately I can't use them anymore, please help me with the easiest way to covert btc to usdt and usdt to btc.