FWIW: When I started preparing my return in January 2021, I was receiving the error that Form 8829 could not be e-filed for CA. A couple of weeks later, I was running scenarios about using the Simplified Method instead of actual expenses, which at the time removed the error, but the error returned when switching back to actual expenses.
Fast forward to mid-February 2021, I was no longer seeing the error when entering either Simplified or Actual BUOH expenses. Since the cost of removing this form was significant, I decided that the ~$10 USPS Priority Mail fee to mail my CA return was better than losing the deduction and having to pay the $20 CA e-file fee.
On 2/20/2021, I used used Actual Expenses to calculate BUOH/Form 8829. I went through all of the steps to e-file Federal and CA State returns without receiving any errors. On 2/21/2021, I received notice that both the IRS and FTB accepted my e-filed returns. So, I'm not sure why the TT CA Forms page still reads that Form 8829 is "unsupported" for e-file. 🤷🏻
