Pulled the 4.27 final release and I’m getting this error as well.
\UnrealEngine\Engine\Source\ThirdParty\Windows\DirectX\include\d3d12.h(427): error C4668: 'WINAPI_PARTITION_GAMES' is not defined as a preprocessor macro, replacing with '0' for '#if/#elif'
Even did a fresh install as I didn’t have any engine customization on my end.
But like scottunreal mentions; WINAPI_PARTITION_GAMES seems to not be defined anywhere, causing the engine to not build.
So yeah, commenting it out seems the only workaround on our end. Feels like something should be done up the chain though.