I agree with @Dianaboston - the fundamental problem is that TT 2020 is not even asking the questions about a second home (or other types of non-1099-B income). If TT doesn't collect the needed information, how can it handle the transaction correctly?
To reiterate, the issue occurs in Wages & Income > Investment Income > Stocks, Mutual Funds, Bonds, Other > Add More Sales. Clicking No (in response to the question "Did you get a 1099-B or a brokerage statement for these sales?") should, but does not, bring up a screen on which you can choose Second Home.
Or, to put it a different way, following the instructions in the Best Answer at the top of this thread fails at the last step. Pretty frustrating!
