No windows OS below Windows 10 is supported on kaby lake. Thus, there are no drivers.
Also, "any help" would be "support", and windows 8.1 is not supported.
Yes I know there is no official support for pre-win10 OS, which is why I posted here. There are various posts in this forum about similar issues and people have gotten working drivers for officially unsupported OS etc., so I hope someone can help me out.
It is true that, in some cases, there are drivers/packages that cover multiple Windows generations and thus can support Kaby Lake on older version of Windows. This is NOT the case for graphics, however. There is no driver for Intel HD Graphics 630 for older versions of Windows (i.e. other than that for Windows 10).