.NET 3.5 did not support TLS 1.1 & 1.2 when originally released. Patches were later released for Windows 7 SP 1 & Server 2008 R2 SP1, Windows 8.1 and Server 2012 R2 and Windows Server 2012. However none of these patches will install on Windows 10. They all give the message "The update is not applicable to your computer".
Is there a patch available for Windows 10? It does not seem to be already a part of Windows 10. I've confirmed this by testing an HTTPS request in a .NET 3.5 app to a server requiring at least TLS 1.1 and it fails.
There is a similar question with good answers but a) the recommendations to make code changes don't work for me because I'd prefer to install the patch, and b) the answer that references the patches doesn't cover Windows 10.