If all three 1098s are reporting different mortgage interest payments (not double-reporting), then enter all three in the Mortgage Interest, Refinancing and Insurance interview.
Enter the oldest one first, then the next oldest and then the last one (from the refinance). Answer the questions carefully.
Enter "$1" as the "outstanding mortgage principal" amount (Box 2, Form 1098 Mortgage Interest) for the two older (paid-off) 1098s. This will keep the program from adding or averaging the mortgage balances and thinking you owed more than you did at any one time.
Entering $1 will not have any effect on your tax calculation and will not generate an error in either TurboTax or with the IRS, From an economic perspective, it is accurate - you owed virtually nothing on these mortgages at the end of 2020, since you paid them off with the refinance.
For the last 1098 (the refinance), enter the actual "outstanding mortgage principal" amount in Box 2. This is what you owed at the end of the year and most accurately reflects your average loan balance for the entire year.
See What do I do if I have multiple 1098s from refinancing my home debt? for additional details on this issue, but following the steps above should avoid any problems with reporting your mortgage interest and principal balances.
