Windows 10 V1909: Intel graphics driver error ‘OS not compatible’

[German]Just a brief  information for people who want to upgrade to Windows 10 version 1909 and try later to install the Intel graphics driver 26.20.100.7323 DCH. It's possible that he installation ends with an error message 'OS not compatible'.

The issue in detail

Intel released the Intel graphics driver 26.20.100.7323 DCH in the middle of October 2019 (Martin Brinkmann from ghacks.net wrote something about it here). In the release notes this driver is explicitly described as compatible with Windows 10 Version 1909 (RTM). 

https://t.co/KNEnYPHZxo@Deskmodder @WinFuture
Die Version lässt sich gar nicht unter 1909 installieren. BS inkompatibel.

— al Qamar (Karl Wester-Ebbinghaus) (@tweet_alqamar) November 3, 2019

Yesterday I stumbled upon a Tweet from German blog reader Karl Wester-Ebbinghaus. Karl wrote in the above Tweet that the driver won't install under Windows 10 Version 1909. The installation ends with an error message 'OS not compatible'.

There are some hits when searching in conjunction with an incompatible Intel graphics driver. The explanations that the operating system is outdated are not really helpful.

The reason for the install error: Intel GPU switched off

After the discussion started on Twitter, Karl contacted Intel directly and asked why this error message occurs. Then there was an answer from Intel, which Karl summarizes in the following tweet:

ok die Sache ist mit Intel per PN aufgeklärt. Wenn die primäre Grafikkarte die Intel GPU abschaltet kommt diese Meldung. Früher war die mal spezifischer. Jetzt kommt "OS not compatible"

— al Qamar (Karl Wester-Ebbinghaus) (@tweet_alqamar) November 7, 2019

So the problem only occurs on systems where the primary graphics card turns off the Intel GPU on the motherboard. Then the Intel graphics driver cannot be installed (which is logically). Karl wrote, that previous driver versions returns a more detailed error message, it the Intel GPU was deactivated. So if you get the above error message when updating the Intel graphics driver, you know the reason.