Minimum system requirements for installing SilverStripe v3.6.1 lists the operating system: Server 2008 R2 as an option:
https://docs.silverstripe.org/en/3/getting_started/server_requirements/
Windows 2008 R2 is in extended support and will cease in 14/01/2020. Is there any known ETA on available support for the later OS versions (2012R2 or 2016) with SilverStripe in the future?