You can deposit something like AVAX as collateral into a DeFi loaning protocol such as Benqi and then borrow USDT. (I actually wasn't loaning out a LOT of USDT on that until somewhat recently.) The general idea is that people are often willing to loan you things if you have enough collateral and are willing to pay high enough interest on the loan.
I'm not sure in general but you can go on the Kucoin exchange and borrow USDT and sell it for USDC.
Also if you don't mind having a position in bicoin you can bet BTC/USDT will go up on the futures market. Actually I guess you could go long BTC/USDT and short BTC/USDC to hedge the bitcoin movements.
I'm not quite sure the costs. I once shorted Tether on Kraken but it was horribly expensive.