Can’t you use a straight mortgage calculator, change the loan term to the remaining time on your loan and look at “total interest paid”? https://www.mortgagecalculator.org/
Isn’t it just as simple as reading your monthly statement? The payoff is the remaining balance. The total of all the payments you have left to pay is the amount including interest. Subtract one from the other.
Just have to find a calculator with an amortization schedule included. Plug in the existing loan conditions then scroll to the bottom for total interest paid.
Does your bank allow you to ask for your payoff number? If so, it might be easier to multiply your monthly payment by the number of months you have left and subtract the payoff. That’s about how much.