I believe in the case of a 1099-INT from a PRIVATE PARTY or if the 1099-INT DOES NOT EXIST then you may have to IGNORE the TurboTax Mis-guidance in the question "Do you have any interest from ANOTHER BANK OR BROKERAGE?" (if/when that question comes up. YMMV. )
I think you say YES here even though it is NOT from a "bank or brokerage".
Plenty of other places interest might come from, TT!!