Google's AI overview provided the exact solution I was looking for. This seems like a known issue with TurboTax where even after indicating that I didn't have an HDHP plan for tax year, it still forces you to select plan type.
The fix to handle TurboTax's "No HDHP" errors per the Google AI overview (which is Gemini) is that even though I had no HDHP plan, I should select "Self" and then marking "None" for all the months in subsequent detail screen. This is a known common workaround and used in past by many users.
