I was hoping this would be fixed for 2024. I had to file by mail for my 2023 taxes. Here is what I did and video instructions as well:
https://streamyard.com/watch/S49rY8byCKVF
I filed by mail because I wasn't able to claim the $500 Solo 401k tax credit via TurboTax online as a sole-proprietor.
I downloaded my TurboTax documents. Then, I filled out form 8881 - adding $500 to Part II, line 9 and 11.
Schedule 3 6Z write in FORM 881, PART II, for the $500. Your total will be on Schedule 3, line 8.
Form 1040 line 20 - write in the amount from Schedule 3, line 8.
