Version 19.1 supports Windows 10 1909. Windows support is determined by the version of Pega Native Foundation installed. We always recommend you install the latest version.
The Pega Native Foundation version that is compatible with version 19.1 is the PNF 10.1 series. The last digit of the version number is the latest Windows version supported. So version 10.1.5.1909 - 10.1.7.1909 all support Windows 10 1909 and our recommended version for you to use is 10.1.7.1909.