I also believe that TurboTax has a bug -- or at least fails to guide the user to do this properly. I do not believe that Schedule D AMT is the correct place to fix this. With the same problem, I went to the Form 6251 Wkst in Forms mode and overrode the line K1, subline 3 entries with the actual numbers that should be there. The regular tax gain from my Schedule D entries, and the AMT loss from my own calculations ((FMV at exercise - sold price) * # of shares; 2 sale dates and 5 different strike prices; yuck). This made a *substantial* difference in my tax outcome from what TurboTax was computing. I was able to recover much of the AMT tax paid on the phantom gain in the year of exercise. Note that in my case I also had substantial new phantom tax gains from the exercise of additional ISOs in 2023.
