My guess is that the "security check" for Windows 11 is based on inspection of a few registry entries. In which case it can easily be bypassed on Windows 10 with a simple double-click of a .reg file, and the original registry settings can be restored by the same simple method.
This assumes that TurboTax for TY2025 is not actually relying on Win32 API properties and/or methods that are specific to Windows 11. Worst case will be if TurboTax is expecting certain hardware or firmware features (such as a physical TPM chip or BIOS support for a fTPM), in which case we may be forced to buy new hardware vs. just upgrading our current hardware to Windows 11. We won't know for sure until we get a copy of the product in hand...
Question for TurboTax Experts: When exactly can we expect Intuit to ship the TurboTax Desktop products for Tax Year 2025?
