You can go from altcoins to #LiquidNetwork on @sideshiftai sideshift.ai
And use @side_swap to store your #LiquidNetwork assets and swap from L-BTC to L-USDt.
On the checkout, verify if both the coupon "maximus" and the payment with L-USDt were introduced and correctly selected. And also don't forget to fill the form with your address.
On #LiquidNetwork, fees are payed with L-BTC. Don't forget to leave some L-BTC on your@side_swap to pay the fees.
Something I didn't do, just to assure I couldn't send my L-USDt out of the wallet.