i may use a different version (desktop so i can use forms mode) and I see where the problem could have arisen. in interview mode (online and also used in desktop) Turbotax does not ask the question "is this a final k-1" but rather the question "this partnership ended in 2019", extremely bad wording on TT's part because I would interpret this as the whole partnership not my interest. without that box being checked you never get the disposal question.
i really don't know how to delete a K-1 in the online version like you can in desktop but you can certainly delete the carryforward info and check that box about partnership ending in 2022. then indicate you sold it for zero or perhaps better see if another online user can suggest a method or contact support.
