There are several ways to take a short position on USDT. You can trade USD for USDT on Kraken exchange. A short position would be depositing USD and placing a limit order under 1:1. This involves locking up capital for the order. If it never loses the peg, you lock up capital forever for 0 gain. You can also borrow Tether via various defi loan markets, but you will have to provide collateral and interest payments.
Both have costs, be it fees, interest rates or opportunity cost. No safe bets in this game, except buy and hold bitcoin for periods > halving period.
It's entirely possible Tether actually have collateral worth more than their claimed 1:1 peg NAV.
The 1:1 peg is arbitrary and since they don't allow direct redemptions they could easily pull a stunt like repricing it to $1.50