Ah, so the T5 is the issue. Weird, it's not at all in the Locked Forms FAQ page.
The T5 has been (and still is, right now) available on the CRA's website since the 13th of December 2024, so unfortunately it seems TurboTax is simply lying when they say the issue is on the CRA's side. My friends have been able to filed with a T5 using different programs, so it seems TurboTax simply hasn't done the work on their side.
