What's funny that besides this it is rock stable, no drops and incredibly fast - I can achieve 450-500 Mbit/s to my Archer C7.
Uninstalling drivers doesn't help also (Windows 10 won't let you uninstall builtin driver 18.x.x)
As you mention, bluetooth works all the time (reboot/poweron)
This message was posted on behalf of Intel Corporation
We understand you're having issues with your Intel® Dual Band Wireless-AC 8260 disappearing after every reboot.
Please keep in mind that custom wireless integrations are not supported. Currently, we only support customer integrations of our Intel® Dual Band Wireless-AC 7260 for Desktop.
- Regulatory Information Regarding Wireless Hardware Installation or Upgrade.
However, we did review the specifications for your motherboard, and were unable to find a reason for your adapter not to work properly. It's possible that you purchased a model that was intended for a low power system, or that your motherboard does not support the power management features used in this adapter.
Since these adapters are intended for OEMs only, there are several different sub-models. Some are to be used with vPro systems, others are low power, others have LTE Coex, etc. You can take a look at this part numbers in the product specifications page for your adapter under "Ordering and Spec information"
- Intel® Dual Band Wireless-AC 8260
Our main recommendation will be to contact your motherboard manufacturer to find out if they have a qualified vendors list (QVL) or a hardware compatibility list available.
I've contacted the manufacturer and they are aware of the problem and they send me beta BIOS which solved the problem completely. So, it is recommended to contact ASRock in any case like this, they will gladly help.