tl;dr: success by first re-initializing the form 1116 (switch from credit to deduction then back to credit) then use the non-simplified AMT calculation method. e-file accepted.
Like a few others have noted upthread, changing to the non-simplified AMT calculation seems to work. In order to get to that point though, I used the strategy of first switching from foreign tax credit to deduction (to re-initialize the form 1116, I guess), then switched back to credit. I had to re-enter one piece of information, and TT also reported an error for a missing date (it was blank, not "various"), but after fixing that, the returns (both federal and CA state) were now accepted. The only price might be dealing with the IRS objecting to not using the simplified calculation for the credit, but the amount came out the same so I don't think it will matter.
