The interest is paid quarterly.   For the first three quarters it was paid to the decedent's checking account.  For the last quarter is was paid to the Estate's account.   I am thinking about reporting it on a "cash bais" to the decedent and Estate.   Therefore the decedents final 1040 will show $60,000 interest income and the Estate will show $20,000 even though the 1099-INT shows the full $80,000 to the Estate's tax ID number.   And add a preparer note as you suggested.  Does that sound O.K.?

The other option would be to split based on the date of death, 08/15/19.  

Recording it all to the Estate does not feel right to me.