Tether has a bad reputation of freezing USDT, if they get notified by the authorities. That is one big risk with USDT and if you are okay with it then you can use any blockchain to store your USDT. Please keep them in a open source, non custodial wallet and not on any exchange. Unstoppable wallet is a good wallet for storing both Bitcon and USDT. It's a mobile wallet and you can take a look by visiting https://unstoppable.money/