The donation of the NetBeans C and C++ features from Oracle to Apache was not complete at the time of the 11.2 release, though it is not far off, and the 11.3 release (January 2020) is scheduled to focus primarily on the integration of the C and C++ features, once they land in the Apache NetBeans GitHub. Until then, go to the Plugin Manager, enable the NetBeans IDE 8.2 Update Center, which lets you install the NetBeans IDE 8.2 modules providing C and C++ features.