I have got a HP Envy x360 laptop with Intel i5 -8250U CPU (full specs). It has got Intel HD Graphics 620 card.
I have installed Windows 8.1 Pro x64 on it. I am not able to adjust screen brightness on this computer. Then I realised that it is the graphics driver issue.
Microsoft doesn't support Windows 8.1 Pro officially which was disappointing to learn as it is not such an old Windows, but I prefer it to Windows 10.
I have read around that there might be a workaround - source question. It seems you can make some changes to the drivers file and disable driver signatures temporarily, and then I might be able to resolve this problem. But I don't fully understand which files to change and how.
Please note it is 8th generation Intel i5 CPU processor.
Could someone guide me please? That will be really appreciated.
Support of only Windows 10 on 7th gen and later processors has been known for more than two years. It is time for you to accept that fact.
There are no drivers for anything less than windows 10. And, hacks as you suggest are not supported here.
Also, if Windows 8.1 was supported on the HP hardware, they would have a driver. But, they do not.