"Does not support Windows 10" is very different than "will not run on Windows 10".
Most likely, it will run and be fine. But if there are any technical problems that would usually require contacting TurboTax Customer Support for non-tax technical support, TurboTax won't "support" it (they won't help with the non-tax technical support because it is running on Windows 10).
Personally, I would avoid the online version.
However, another thing to consider is if you really want to have your tax returns on a computer with Windows 10, regardless of what tax program that you use. Windows 10 will no longer be getting security updates from Microsoft (except for certain circumstances, such as paying a fee). Do you really want to have your highly personal information (such as tax returns) on a computer that doesn't get security updates anymore?
