I am using Cisco VPN Client v5.0.07.0440, which needs the same minor registry edit on Windows 10 that it did on Windows 8. On Windows 10, it also requires installation of a Dell SonicWall driver before it will work correctly. Once it's set up, it works great.
When I installed the Fall update for Windows, it automatically uninstalled this Cisco VPN Client citing compatibility issues. After I reinstalled, it worked perfectly again. I am not sure how Microsoft makes the decision to uninstall something automatically. Even though the configuration is not supported by the vendor anymore, there are many people using this legacy Cisco VPN software.
This is an example of Microsoft uninstalled some desktop software that was working perfectly fine. At least they didn't block the reinstall!