You don't need a Form 1098 to enter the interest.
Please see this answer from DawnC0.
A camper or Recreational Vehicle (RV) meets the IRS definition of a second home if it contains sleeping, bathroom, and kitchen facilities. A home includes a house, condominium, cooperative, mobile home, house trailer, boat, or similar property that has sleeping, cooking, and toilet facilities. Interest paid on a loan for the purchase of a recreational vehicle is, therefore, tax deductible as valid home interest on a second home.
For you to take a home mortgage interest deduction, your debt must be secured by a qualified home. This means your main home or your second home.
You can enter these deductions under Federal Taxes > Deductions & Credits > Mortgage Interest, Refinancing, and Insurance (Form 1098). Even if you don’t have a 1098, you’ll still need to enter the requested information from an alternate source, such as your mortgage lender or year-end mortgage statement. In that case, just enter everything when prompted as though you have a 1098. (Because you’ll be entering the equivalent of the amounts from the different numbered boxes of the 1098 without actually having that form).
For confirmation, please refer to IRS Publication 936, Page 4, left column, first paragraph, under the heading Qualified Home, here:
