It turns out that last year, the same exact issue was reported -- without a solution:
https://ttlc.intuit.com/community/taxes/discussion/issue-with-form-8938-for-2021-foreign-entity-or-i...
I managed to workaround it by going again to Form 8938's entire interview process (there is no way to directly edit the forms), not modify anything, just click continue, continue, etc. until done.
This appears to have worked around the bug, because immediately after that, TurboTax took me to e-file, sent it to the IRS, and 29 minutes later I received another email from `TurboTax at Intuit` that "Your federal tax return was accepted by the IRS".
All is well now. 😊
